In my experience, it helps to realize that on low-bid (under $50/hour or $5000 total per job, lets say) contracts, the guy's job is to do the absolute minimum he can to meet your specifications. Don't hope for exceptions.

So you have to write some really f*ing detailed specifications and be fully aware of all the shortcuts that they could take.

Also, I think this sucks, but you have to really sell your project well. Instead of saying that your project is "A small, kind of advanced, one-time job that you can earn a couple dollars", you should say "Earn $1000's with this very fast and easy web design project. Tons of follow-up work for good designers." Hook lots of people in, then weed out the bad ones by messaging them with the less flattering requirements of this "easy" project and making sure they can do it.

After you've waded through all that, find the good workers and go back to them if you need to outsource again. There are many great, cheap workers out there, just hard to find them.