going to the track for my first time

It was fun my first time was 15.537@87. 2.1 60ft my last pass was 14.87@92. 2.01 60ft

With my street tires they spun but gave me the best time 245/60/15 and the rest of the passes were my 28/9/15 slicks so what would work best is 26/8/15 for me