Compared to others on here my experience is very limited, but one thing I would say is that when I started out (mainly in Tri) I threw quite a lot of money at buying aero kit (it still gives me a massive buzz to go out on my disc etc) but I'm starting to wonder if that money mightn't have been better spent on tools that would help me train to become a better athlete (eg. getting a power meter in a training wheel and a cheap disc cover).
Training tools >>>> aero bling (unless you're a slevless, of course ;o))
Training tools >>>> aero bling (unless you're a slevless, of course ;o))