To my knowledge almost all Saltwaterfish are wild caught.
I don't know about the rest of the world but in the UK quite a few Clownfish, Gobies and a few others are captive breed.
Many others though are still wild caught. Also doesn't mean they shouldn't get the best care possible.
I would say you could possibly have a single clownfish in a 15G but you are very much on the lower limits and I don't think I would would want to keep a pair in less than 20G.
As I have mentioned before I don't consider Clownfish to be reefsafe so I would not keep them with any corals. Clownfish like to "host" things. This basically means they rub against whatever object they pick constantly. Often this will be whatever your largest coral is. Once that gets killed off they will move to the next largest.
Also for the budget you previous gave I'm afraid it's not really high enough to run a marine tank right now.
Quick rundown on some equipment:
$120-200 Decent lighting - Even for soft corals you need decent lighting.
$130 Live Rock - You will need at least 7KG of liverock. Prices may be different where you live but in the UK its currently about £15-17/KG
$80 Powerheads - You need ideally X30 water flow, however you also need redundancy and to make sure they is no dead spots so at least 2 small powerheads.
You then also need Salt, RO water, test kits, refractometer, etc. Your $90 budget unfortunately will not even cover these bits.