How many Prismatic Philters and Health Philters would I need to to eventually breed a max start offspring if I start off with four pairs from essences? Just trying to figure out how much of what I need for my project.

depends
> What rarity of essence (regular or enhanced/mystical)
> fabled or regular species
> how many pets are being generated to start
> # of traits
> RNG luck

Generally you do the traits first (so you can just leave out all offspring that don't get the good rng); if it's just a 2v project and you're starting with three enhanced/mystical essences, then you can just have the traits immediately, but in other cases that part would take longer, so you'd get some nurturing on the generations that are working towards the traits before starting on stats

In terms of prismas, if you were starting with a set of enhanced/mystical fabled essences and traits aren't a factor...
we can say the average starting base stats will be:
HP: 285
Mana: 120
str/int/dex/agi: 38

So with prismas boosting 200 / 10 / 10(x4), and the max being 2000 / 200 / 100(x4)

6-7 generations for the four base stats (depending on how many nurtures you're getting)
8 for mana (mana cannot be boosted via nurturing until all other stats are max)
8-9 for HP (again, depending on nurtures)

so (assuming 4 breeders per generation) 8x4,
meaning something like 32 prismas + 4hp (again, this is starting with 4 fabled species enhanced/mystical essences, and assuming traits aren't a factor so the stat boosting starts from the offspring of the g1's (if traits are a factor, then maybe a little less if nurtures are gained in high enough numbers?))

(I don't claim to be either a math master or great at a linear project starting at essences, but this should be a decent overview)

Does the essence matter in terms of the base stat the parents will start with? Or can any essence be used?

yes- Fabled species naturally have higher base stats than regular species (puffs are a regular species and only pseudo-fabled for their rarity), and enhanced/mystical essences have higher stats than regular essences; hence why we were specifying that the best outcome for amount of philters would be with enhanced or mythical fabled essences

copying and pasting from our guide to generator essences:

"Regular Essence Regular Species Generated Stats:
HP: 150-180
Mana: 90
Other: 12-30, averagely* between 14-18

Regular Essence Fabled Species Generated Stats:
HP: 195-225
Mana: 110
Other: 21-36

Enhanced/ Mystical Essence Regular Species Generated Stats:
HP: 200-220
Mana: 100
Other: 16-40, averagely between 20-24

Enhanced/ Mystical Essence Fabled Species Generated Stats:
HP: 260-300
Mana: 120
Other: 28-48"
(obviously the exact stat distribution depends on the species and the * there next to the 'averagely' is about luffox whose ludicrously high speed is an outlier)

Alright thanks. I am wanting to go with a Luffox or Faelora. So looks like I am going to be making this harder on myself lol