Tea tree oil works pretty well for me. I've only been using it for about three weeks, but my face has cleared up by about 80%. It's pretty inexpensive. You can get it on the internet (probably cheapest option), or at natural food stores, at least in the US. I bought an 8 oz bottle (probably 6-9 month supply) on the internet for 16 bucks including shipping. I used to use Differin, Minocycline (antibiotic), Cleocin lotion, and benzoyl peroxide (all prescription), and now my face is only slightly less clear than it was using all of them (Cleocin is the only one of those I'm still using), so I would say tea tree oil is pretty effective! I really don't have any scars, so I don't know if it would help with those.

Tamanu oil is supposed to be good for healing scars. I've found it for about $20/oz on the internet (it's expensive, I know).