My first choice would be a stock, original Russian SKS. That is mostly from a historical perspective. Figure to spend no more than $300.
However, you can buy two chinese SKS's for the cost of the above mentioned Russian version. The Chinese rifles are as good as any made. I prefer the screw in barrel, but the pressed in barrels function just as well. You should be able to find a very good Chinese one for about $150.
The Yugo is my 3rd choice. It, to is a fine weapon. But the g-launcher is good for display and not much else. And unlike everyone else's SKS, the Yugo do not have chrome lined bores. However, they can be had for les than $125 just about everywhere.
Buy good quality and condition. The source nation is meaningless if the SKS is beat up/pitted or it has an aftermarket magazine.