A bit late to the party here but the three biggest things that can help:
Clip-on aero bars
TT helmet
Skinsuit
Tyres/tubes
That’s where you’re biggest bang for your buck will be found. The more expensive upgrades (TT bike/wheels) will make you faster, but the margin of gains won’t be as much as those cheaper options.
There are things you can do to make yourself as aero as possible such as paying attention to not having pockets (or race numbers!!) flapping about. Why go to the trouble of getting aero then attack a sail. If you need to carry things, think of the most aero way of doing so - eg minimal essential spares in a saddle bag rather than pockets or top tube bag.