3rd Gen Crobat Moveset Between

Okay like an idiot I used my 'Sludge Bomb' on my Tentacruel pretty early in the game since his movepool was pretty awful at the time

Training a Zubat as we speak, now I'm stuck on what moves it should have, not competitive just trying to complete Pokemon Sapphire for my 2nd time EVER since I lost it years ago and just recovered it recently:

It has to know FLY (obviously), but what should the other 3 moves be out OF:

Shadow Ball
Confuse Ray
Ariel Ace
Poison Fang

And whatever moves it is possible to learn, Only 3 can be picked what would the best 3 be especially for the Elite Four

,Thanks due

Fly
Poison Fang(Give it Steel Wing until it learns it)
Shadow Ball( only if you don't have another option to take down Ghosts and Psychics)
Confuse Ray