i got two sets of tires with the kart when I bought it. one set clearly didn't have much wear, the others were new in wrappers with stickers. i factored the cost of these tires into the deal...wound up being a mistake.
the used tires were absolutely worthless, no grip no matter how hot they got. dozens of spins later I gave up on them. the new tires were "medium-hard compound" which is supposed to last a long time and be good for practicing. they decided to shred and peel off big hunks of tread almost to cord the first time they got used.
good, new tires are probably the best present you can give yourself. falken azenis are about the best deal going, lots of stick and really cheap. if they make a size that will go on your car, it's worth it.