I struggle with Cleric, I appreciate the things it brings but I often find it one of the least interesting casters, now you may have seen this build before but every version I saw seemed to focus on Sorcerer first and going in on Charisma when I was trying to enhance the Cleric aspect.
Start Tempest Cleric
Levels 1-4
Typically Cleric leaves a lot to be desired early game, it lacks the spells that carry the other casters at level 3-4, no equivalent to Cloud of Daggers or Moonbeam, but Tempest at the very least has the ability to buff the damage of spells like shatter.
Get 2 handbows because the martial weapon proficency of tempest lets you wield them and this makes a lot of difference on the feel of the early game to play because now you have something to do every turn with that bonus action.
Level 5
Now here's where the standard Cleric is considered to shine, Spirit Guardians is an incredible spell but there are so many fights where the enemies where too far or where it would be too risky to send the Cleric to greet them and that's where Call Lightning come's in, amazing little spell, scales very well, is lightning damage and it pairs amazingly with elixirs of bloodlust and potions of haste which I favored more as the game went on, by level 9 the character could quite easily drop 4 call lightning in a round because once cast the reactivation is free for a round.
Level 6
Your lightning and Thunder spells can now knock back enemies, you have basically have an at will area of effect damaging knock back, which synergises very well with classes that have strong crowd control that use spells like Spike Growth and Hunger of Hadar. You can also maximise 2 lightning or Thunder spells.
Level 7
This is where you respec and take the first level of Sorcerer, Storm will get you the best feature at level 12 but Dragonic will offer slight increase in survivability, after that take Cleric to 6 again, this will provide con-proficiency and as Cleric is now your second class it will let your items scale off Wisdom. Shield will greatly increase survivability and magic missile is nice utility.
Level 8
Second level in Sorcerer provides metamagic and with it, extend, extend combined with Clerics command offers one of the best forms of Crowd Control in the game and a major reason why I favor Wisdom over Charisma.
Level 9
You now have quicken, which pairs extremely well with Call Lightning, 1st round of combat with a bloodlusted elixir you can use 1 spell slot and 3 sorcery points to drop 15d10's worth of electric, 30d10 if you have someone set up some water. The build is essentially complete now and you're just picking up extra's.
Level 10
Feat from Sorcerer Wisdom to 20 if you didn't use Ethel's hair
Level 11
Get Counterspell for Sorcerer, an important defensive option, especially on Honored mode.
Level 12
This is where you're best being a Storm Sorcerer or respeccing to Storm, the ability being separate damage allows it to double on effects that trigger off damage.
Spells
Now it doesn't mean the spells I listed can't be great, just these are the one's I got the most milleage from
*for key must have spells at least for their level
** for key spells for the game
Cleric first
Level 1 cleric spells
** Command from Cleric, non-concentration crowd control, becomes a lot stronger when you can extend it. Turned Grym from a tricky fight to a cakewalk
** Create water, must have for the build, although when against single opponents or when they are tightly bunched a water bottle will do the trick. On honour mode some fights like the Bullette and Beholder go way smother with this.
Thunderwave. Your bread and butter damage spell at level 2 as now you can maximise it once a fight
Bless, extremely useful for early game when accuracy is a real issue, drops off heavily as concentration slot becomes a premium and you find so many ways of increasing accuracy
Healing word, very useful for helping downed allies at range as a bonus action
Inflict wounds, more of an emergency, you don't like to be in melee but sometimes enemies don't give you a choice so you may as well do premium damage.
Guiding bolt, does good damage for the level
Level 2 Cleric spells
Shatter, your new bread and butter for levels 3-4 because it can also be maximised, can be cast and range and is easier to place
** Aid, at low levels you won't have the spell slots to spare but if you aren't camp casting this becomes an excellent safety net as the game progresses, especially handy for summons.
** Enhance ability, a must have for honour, can turn the chance of failing a check from 1/20 to 1/400, works best if you have both this and another character with guidance.
Blindness, can be nice control at early levels for enemies immune to command
Spiritual weapon, can sometimes be handy to drop an extra body into a fight and its main value is that its a bonus action, later when you have other summons who stick around, its value drops hard.
Silence, main use is it can shut down casters if well positioned with no save, situational though.
Level 3 cleric spells
** Call Lightning, key spell of the build, damage can be maximised with destructive wrath is lightning so is doubled with wet, it almost removes one of the biggest weaknesses of casters which is resource issues. Any long fights with lots of enemies become a call lightning fest. When you get a certain ring it can even apply radiant orbs
** Spirit Guardians, very useful running around spread out enemies and applying radiant orbs before you get the callous glow ring.
** Glyph of Warding, has a large area of effect than Call Lightning, scales better than fireball, doesn't use concentration, but most importantly it lets you pick your damage type, this is a critical spell for dealing with lightning immunity or taking advantage of enemies that may have fire vulnerability, its sleep version can also be amazing no concentration area crowd control. If the opportunity presents itself you can even cast it before a fight if you know an enemy will walk into it. Just generally a great spell and every caster who can prepare it should. Only downside is it can't be maximised.
** Animate dead, hard to justify when you first get it, spell slots are at a premium but as you progress they provide free bodies for harder fights, can be especially useful to bait enemies who have abilities that trigger when hit
** Mass healing word, special case, whispering promise and hellrider gloves paired with this are a very powerful combo, blessing and blade warding but that will require your first bonus action and those items slots from this point on, but this is something others can do, a Crown Paladin is particular well suited to this role if you have a Paladin in your party.
Sleet Storm, nice crowd control, can pair well with Hunger of Hadar, does require concentration slot though
Daylight, situational spell but it doesn't require concentration and it can be very useful against certain enemies.
Remove curse, very situational spell but there are some really nasty in combat effects in can help with.
Sorcerer
Level 1 sorcerer spells
** Shield, amazing defensive spell
** Magic missile, some annoying enemies make this almost mandatory and it can be brutally effective with cull of the weak.
Chromatic Orb, can be twin casted, excellent little spell. But you've neglected charisma I might hear some of you say, as the game goes on accuracy becomes boosted so easily that this becomes a non-issue against all but the highest ac opponents.
Special mention, Witchbolt, same deal as chromatic orb, you may think about the lack of Charisma but it is an attack roll, not spell DC, and because its an attack roll it can crit, this can do crazy single target damage but in practice with how often I could drop chain lightning I never found I need it.
Level 2 Sorcerer spells
Cloud of daggers, no save, force damage, requires concentration slot though
Darkness, can be situationally useful although I prefer others classes take this role.
Level 3 sorcerer spells
** Counterspell, a situational life saver which can stop some really nasty effects from ruining your day.
Haste, I listed this for those that swear by it, but your concentration slot is highly valued, but its a fun alternative for non-risky fights when you twin cast it, but you will mostly be using potions of speed
Equipment
** for equipment that stays on until the end
Act 1 gear
Weapons
hand crossbows, with 16 dexterity you can be a decent archer, special arrows are plentiful and you get a bonus action attack
Melfs acid staff, this is a +1 spell DC save stat stick for a large portion of the game
Armor
** Luminous armor, you know it, you love its affect, you hate its look, I mod in some nice looking outfits and switch the equipment to always show camp clothing for this one.
Headgear
Haste helm, this is for Spirit Guardian because you need good speed to get the most of it.
Shadespell Circlet, when you're not using Spirit Guardians as you need to be in darkness to get that +1 DC
Rings
Crushers ring, more speed means more spirit Guardian victims
?? Whispering promise, very strong effect, blessing everyone you heal, I don't want to list it as mandatory though, it really helps the party but its not required for what the build specialises in
Ring of protection, nice defensive boost, but may be better on front liners
Footwear
Boots of speed, amazing for Spirit Guardian
** Boots of Stormy Glamour, you eventually just auto apply reverberation with every spell, although the boots of speed can be more valuable in the earlier game
Gloves
Gloves of belligerent sky, same as the boots of Stormy Glamour, just auto apply reverberation, but gloves slots tend to be more valuable so this isn't an auto pick
Gloves of dexterity, possible end game pick, it gives extra initiative, accuracy increase and can frees up stats
Amulets
Amulet of misty step, useful in a pinch
?? Pearl of power amulet, this is one you use out of combat to restore a third level spell, very useful early game
Shield
Adamantine shield, your shield until the end of act 2
Cloaks
Highly contested slot in act one so you will know best on who gets what few options you find.
Act 2 gear
Weapons stay the same
Armor Stays the same
Amulets stay the same
Gloves stay the same
Rings
** Callous Ring, not every spell does radiant damage and applies radiant orbs and reverberation
?? True loves caress, can be useful for warding bond from a tougher class like Barbarian or Moon Druid, you can cast the spell and then unequip it
Caruscation ring, more radiant orbs, but I find this can be overkill
Headgear
Fist breaker, gives more DC and initiative, great headgear
Shield
Sentinel Shield, huge boost to initiative
Cloak
Still contested, everyone wants them and nothing stands out for this build yet
Act 3 gear
Weapons
Markoheskir, a staff so good and does so much that if it wasn't in the base game you would think its some overtuned mod weapon. Improves spell DC, electric damage, extra spell, free twinned chain lightning every fight, this is your weapon, use it, no other class gets it
Bow
Hellrider long bow, you want that initiative
Shield
Ketheric shield, a +1 DC save stat stick, simple, effective.
Headgear
Hood of the weave, a big +2 bonus to your spell DC saves
Armor
Your wearing Luminous, you can wear other armor if you want but you forgo a lot of defensive protection for the party for +1 spell DC
Gloves
**Stick with Belligerent sky, the reverberation typically offers more than +1 spell DC and those are typically tied to contested items
Footwear
**Stormy Glamour
Amulet
Amulet of the devout, this is yours, +2 spell DC and you've got the best channel divinity in the game, it was made for this build.
Illithid Powers
Black Hole which makes the build so much stronger as long as someone uses it, I would actually save tadpoles to make sure everyone has this, it bunches up enemies for Call Lightning and an overlooked aspect, slow stops reactions, enemy counterspells are the bane of your existence and this can stop them before they happen.
Consumables
Bloodlust Elixirs, buy these whenever you can, for your build its almost always a free action every round.
Potions of speed, its much safer to use than the spell, as it doesn't risk the loss of a fight if concentration is broken..