I'd say go for a Psion. I mean, if you are going to be in a psionic campaign, you might as well go for the gusto. They start with a small number of powers, and gain 1 or 2 per level, so there is time to learn how they work as you go. Psions come in 6 "flavors", so pick the one that matches what you want to do (personally, I like the Shapers). The only slightly complicated parts are feats and augmentable powers. Feats I deal with below. Augmentable powers you can learn as you take a power that is augmentable. But don't always augment your powers to the max or you will run out of points too soon (see below).
Now for simplicity, I suggest you take a human, and for every feat you get (bonus feats, regular feats, the free human feat), get the feat that gives you extra power points. [Psionic Talent is the name of the feat]. This is for two reasons: 1) It means that you don't have to worry about complicated feats, and 2) It is very easy to run out of power points. One way to minimize this is to get more power points. The other is not to "blow you wad" in every fight. Husband your points like a miser, for when your party really needs you. In fact, write in a big red felt pen at the top of your character sheet: "Husband your points like a miser!!!!!" so you don't forget this vital fact.
The one feat you might consider instead of one of the Psionic Talents is Psionic Body, which gives you hit points (which Psions are weak on). And there is a nice synergy between Psionic Talent and Psionic Body.
Now there are other cool things you can do with feats when you get more comfortable, involving either maintaining or expending psionic focus, but I wouldn't worry about that part yet. Just keep your concentration skill topped up (for manifesting on the defensive, if nothing else) and if, once you are more comfortable with the character, you want a different feat from Psionic Talent, you can look them over.
There is a magic (ok, psionic) item you want to find called a Crystal Capacitor (basically, a free shot of power points). But that comes later. In general, crystals are abundant in the psionic items.