A Saiga or a cheap Cetme would be about the only choices available in your price range. The saiga is a solid rifle, should serve you well.
Trying to buy a cheap autoloader in .308 seems a bit odd to me these days. If you're going to shoot it, you'll spend more on ammo than you did on the gun in a big hurry. Even the cheapest steel cased stuff I can find (silver bear) costs me 38 cents a round, and I was quite happy to find that! The days of cheap surplus .308 are long gone.
Might I suggest that you consider a Garand from CMP, and a few cases of their Greek surplus 30-06?