Well I started last July and only got two club races in at the Track at Centennial (MG Yellows).
I ran two races and some practice time and the tires still have plenty left to them.
I’m sure they will have lost a little bit of grip, but until you start getting within 3 or 4 seconds a lap of the leaders I doubt that you will notice much difference at all. In that last 3 or 4 seconds there is paobably a lot of difference, but just learning to drive well will take a good number of laps.
Having said that for new or used tires what I can comment on is different tires. I’ve practiced with Bridgestone YHCs that are stiff whereas the MG Yellows are a lot softer and stickier. I made a big mistake in saving that first lap for qualifying with the new MG Yellows. They were Sooo different from the YHCs that I could barely drive them and had poor qualifying times. The MG Yellows are great but they are soo different that you will want to get your kart setup and get used to them prior to a race.
I suggest getting a spare set of hubs and running two sets of tires. Use the older set for practice and the newer set for a race. I doubt that you will need a new set for club level racing until you start getting fast. For a relative newby a set of MG Yellows should probably last for two or three races and practice in between. I’ve heard you can stretch the life out a bit by rotating the tires from side to side as the insides or outsides tend to wear more and rotating balances out the wear pattern