I'm sure someone is going to ask or is thinking it so i'll be the first one to say it
It depends on the type of budget you are on but when i was starting out i went as cheap as i could get just to make sure that i liked it and wasn't wasting my money. (NOT a waste of money) now i spend to much $$

first thing to get is some sort of safety slide system for your arrows.
don't go without one. ams makes one like.

for example you can prolly get a whole kit made by bohning bowfishing kit for about 30 bucks otherwise you can get just the reel for around 15 arrows for around 10 i'm a fan of the muzzys points.
arrow rest for about the same as an arrow (however you don't have to have a rest but it does make it easier for several years i used a golden key flipper rest and just held it up with my finger works but buy a rest.
I don't use sights never have (maybe i should. I've never got to hang out with any of the pros from illinois so i can't answer for them)

take a look at a few bowfishing websites they will give you an idea of the stuff you need and some prices
ams has a site, muzzy, and try sullys, also you could try basspro.
sorry not trying to push any one product or site just trying to give some ideas of where you can look.