A couple of points
A cocker "will" hit 18bps quite easily, BUT you have to know them, understand them, and have the patience to set them up "properly".
A trilogy uses different parts compared to a "proper" cocker, and it is simply not worth upgrading.
Pretty much all tournaments are capped at 12bps these days so it's a pointless exercise anyhow.
Even the cheapest guns will hit 12bps with ease so buy what you like
Don't buy an egg as they will struggle to maintain 12bps even with a Z board, and if anything your egg will slow your gun down.
Egg advertised BPS rate is complete "Bull", and if you don't believe me, put one over a BPS chronie.
You seem fixated with upgrades which at your point in the game is completely pointless. Buy something stock, keep it stock, spend your money on paint.
A stock "
insert name of your choice" will hit 12BPS out of the box, so why bother changing a thing until something breaks or you at least "NEED" to improve something.
Go play, listen, learn, enjoy