The hallmarks of a dead-typical solid Eldar list are:
-everything (except pathfinders) in a transport. The little point that isn't obvious here is that if it's a non-vehicle in the Eldar codex and there isn't a good reason to put it in a transport...don't take it.
(Everyone has their own exceptions to this. I like Warp Spiders, some people swear by their Dark Reapers or outflanking Striking Scorpions...I'd suggest that you try any and all of the less solid units out by proxying them. All I'm suggesting are things that you will probably use.)
HQ: Assuming you plan to field at 1k points or more, Farseers are by far the most common choice. They're very good, and not very expensive. You may also want to try Eldrad. You will see other HQ's, particularly double-Autarch builds that use reserves a lot.
Troops: By far the most common troop is Dire Avengers, in one of two setups:
1)Squads of ten. You probably have an Exarch with dual catapults and Bladestorm.
2)Squads of five, no upgrades. These squads are taken to make transports count as scoring. They almost never get out.
After that, a squad of (depending on the total points value) 5-7 Pathfinders can sit in cover, piss off monstrous creatures and generally not die except to flamers or cc.
Elites: Okay, close combat choices, cool. But the most common choice out of Elites are Fire Dragons. One (or more) squad of 5-6, in a transport (wave serpent preferable), there to blow shit up.
Heavy Support: Falcons and/or Fire Prisms are the most popular, with Fire Prisms pulling ahead. Obviously, you tend to field Prisms in pairs (sometimes three at a time).
So I'd buy through of all of the above, getting a wave serpent or *maybe* falcon for everything you need to transport. Any and all smart ideas that go outside that, proxy test first. It's not even that there aren't other great things out there, it's that most of the lists people come down to revolve around these options with a sprinkling of other choices.
The only exception I can think of is if you want to field a jetbike army. Well, DA's and rangers won't do you much good. Hold off on buying and proxy, because eldar jetbikes are a little strange.