Spend your money on training. You'll get the most bang for your buck.
After that, aerodynamics matters the most. Aero bars will provide the most. Then the helmet. Then a skin suit. I think aero booties are more beneficial than aero wheels. I could be wrong, I don't entirely remember the article. It was written by some engineers at Stanford. I think.
+1 Best Advice. BTW, it was MIT.