Draw 3 equidistant lines through the tire's "shoulder", from the sidewall to the tread. After your run, you will see how far your tires are rolling over by how much shoe polish is worn away. If it's past the shoulder and onto the sidewall, then your tire is rolling over too much and you need to add air. If it's still present past the shoulder onto the tread then you have too much. If it lines up right where the tread and sidewall meet then you are getting the most traction out of your tire, as it's using the most possible tread in hard corners.
Don't waste another minute waiting on parts, or anything else. Just get out there and start racing! You will suck at first, and you will be slower than many other cars, but the only thing you will regret is not starting earlier...