What traffic source has the highest conversion rate and can do self sign up

Im looking for provider who can give me a good rate for self sign up

Google..
Converts like crazy and all organic

You can try udimi.com

I know organic converts belter because I saw it myself but the paid traffic is a little tricky. I spent more than $1000 in Fb ads but earned way less. In my opinion you shouldn't play with paid traffic with a couple of your bucks. But if you mean a couple of thousands, then go for it. Because paid traffic involves lots of testing which requires lots of $$$$$