Time Trial / Time Trialling / TT

Definitely get the aero helmet first, much better VFM. Then a skinsuit, then wheels. Or wheels first, cos they look and sound fast :) Play around with your position as well, Adam Tophan's book is pretty good at explaining how to get a decent position and is a very good general guide to TT'ing IMO.

I would test positions first and buy an aero lid that suits the position you come up with. Some helmets work better than others depending on your back and how much you can drop your head, etc.