questions

about what lvl would i need to build a bot to sell it for 30 USD?

Unless it has an absurdly high amount of wins, probably at least level 130.

has to be a freaked build i take it? or just a nice solid build like 140 blasters?

For most people nowadays levelling is so fast, you're probably better off getting a ton of wins. I know personally i'd rather buy a level 80 bot with 20k wins than a level 150 with 3k for example.

I agree with Rivan. I'm just interested in buying bots with lots of wins and few losses.

what about say a decent lvl with decent wins? like lvl 120 with 10k wins?

The more the wins, the better the value.