Any way to optimize this idea:

I will rush at people and cast fireball, then I will use sculpt spell to avoid receiving damage. Any additions?

There's no advantage to that. Being closer doesn't increase the damage of fireball.

Prepare misty step or other "escape" spell to get into/out of the blast zone.

A simpler method is the Thunder Step spell.

Honestly, my thought for this would be 4 elements monk or arcane trickster rogue. Both classes get Evasion. Play a Teifling for fire resistance.  Scenario a) you fail your dex save. Evasion halves it and resistance halves it again to taking 1/4 of fire damage. Scenario B) you take no damage.

The main downside to this approach is you wont be getting access to Fireball until much, much later than something like a sorcerer

Quote from Halfastbracegirdle >>

There's no advantage to that. Being closer doesn't increase the damage of fireball.

 True, but you never know when the caster is going to find him/herself in the middle of an ambush with no convenient means of escape. 

Quote from Kaboom979 >>

Quote from Halfastbracegirdle >>

There's no advantage to that. Being closer doesn't increase the damage of fireball.

 True, but you never know when the caster is going to find him/herself in the middle of an ambush with no convenient means of escape. 

 
Yeah but the point is: there's absolutely no advantage whatsoever of deliberately running into melee to cast fireball instead of casting at distance when able to. If anything, it will be worse for you because you're stuck in melee for a round unless you risk an opportunity attack.

Making yourself vulnerable to your own spell reduces the effect of Sculpt Spells, which is normally there to allow you to drop giant AoE fragbombs on your own frontliners without fear, scraping weenies off them and helping them out.  Taking up one of your own Sculpt Spells slots deliberately is weird.

This is the sort of thing you keep in the playbook for when you can't get range, or when something else forces you to cast on yourself.  It's not something you actively pursue.  But yes - get fire resistance, get good Dex saves.  You could theoretically use this as a very precise trigger for Contingency - "Contingent Spell takes effect when I become the target of my own Fireball" - but how that would be useful I don't really know.

Quote from Belca4 >>

Any way to optimize this idea:

I will rush at people and cast fireball, then I will use sculpt spell to avoid receiving damage. Any additions?

 Sculpt spell isn’t able to protect the caster, it specifically says it protects “other” creatures.

Resistance from a racial option like tiefling or dragonborn might help. The new rabbit race has a feature for dexterity save boosts. Being a yuanti pure blood or satyr would give you advantage vs all of the spells saves you include yourself in. The shield master reaction would be able to be used on a passed dex save to reduce the half damage to 0. Resilient dexterity would potentially give you an additional modifier and proficiency on dexterity saves.

if you were a sorcerer you could take the dodge action and then quicken the fireball to give yourself advantage vs the Dex save.

a weird one is the mage slayer feat. Technically you would make yourself roll a constitution save to maintain concentration at disadvantage if you damage yourself. Technically you’d also have advantage against any spell save you target yourself with. You’d also technically be able to use a reaction to make a melee weapon attack against yourself when you cast a spell…

theres probably more but that’s all I can think of right now.

I get it's weird to do it when you can do it in range. But I want to do like aa pyromaniac that wants to "burn with those he baptizes in the flames". Resistance is good but I still get damage, dodge is great and I thought about it but it takes to long to get both a good dodge and a fireball. I though about the sorcerer's ability with quicken spell but that still gives you a change to get hit, it just lowers it. 

I wish there was a way to get immunity to flames

It’s a high level spell at 6th level, which means you can’t do it very often, but tashas other worldly guise can give fire immunity and several other benefits too.

investiture of flame is also a 6th level spell that gives fire immunity, but I think it’s pretty much just a worse spell.

Its not nearly as reliable but you could be a yuanti pure blood who casts fireball and uses the transmuted spell metamagic to change the fire damage to poison, and you’d be immune to it. Mechanically it would be weaker cause poison seems to be more resisted, but thematic my you could just still say it’s fire. 
  it would atleast be poison that targets dexterity save, so that’s actually a slight buff to poison since they almost universally target Constitution saves which creatures are usually good at.

I think one of the UA dragonborn gets to have immunity to their chosen element for a few minutes. That could help.

Also, you could possibly run in, grapple a creature, then restrain them wih the grappler feat. Now you cast Fireball on yourself, and they have a disadvantage on the save.

Extra points if you're a Wild Magic Sorcerer who happens to roll to cast Fireball on yourself at that moment. Usually it's an awful roll, but if you have immunity and they have disadvantage, it actually becomes an amazing roll.

The only quibble I have is that someone looking to avoid the damage isn’t really a suicide bomber.

Thats why you instead cast delay fireball on a tunic, put it on a thrall, and make them run instead 

Or, again, just cast it from afar or risk the dex save to throw it.