ABS Is definitely the cheapest way to go. Although you'll need to cut it yourself unless you buy some ABS tires off ebay, they last forever.
Sushi drift tires sells his through ebay. He rounds the edges too, which helps in the look/uniformity of the tire. They go for pretty cheap too
Those Yokomo tires I hear are very good, but the rings wear out. I wouldn't let that discourage you though, because they should drift really well.