Psionics tend to work well in general.
Ardent
The strange Ardent power-gaining mechanic may or may not let you take higher level powers than you normally could using things such as Earth Power and Overchannel. This pegs Expanded Knowledge to a higher level, giving even more options. That said, if this trick is legal by RAW it deserves the nerfbat.
Astral Construct
Anyone can get level 4 Astral Constructs with Earth Power or Overchannel
3 levels of Wilder, Practiced Spellcaster, Earth Spell, and actually knowing AC gets you level 5 Astral Constructs
Midnight Augmentation and 2 more essentia from anywhere also gets you level 5 ACs without the Wilder levels.
Stacking all of the above (save Earth Power) allows level 6 ACs. These are CR7, and the first to get multiple attacks.
Truly pull out all the stops and with the right item, you can get level 7 ACs (Wilder 3, Earth Power, Psicrystal Containment, Midnight Augmentation, Improved Essentia Capacity, 2 essentia from anywhere, and a Torc of Power Preservation). These are CR8, and the first to get a menu C ability.
Earth Power
This feat is simply amazing at low levels. It's the whole package: more raw power (due to higher augmentation) and more endurance (everything is cheaper). The drawback (that it only works while touching the ground) doesn't tend to matter, because you're not flying that often at these levels.
Expanded Knowledge
Cherry-pick powers below your highest power level.
Midnight Augmentation
By itself, it's like Earth Power for only one power and costing your focus. You can get it up to 3x Earth Power, though.
Psicrystal
Big Guy's with Me provides a great use for the large number of feats, though he's likely to be on the wrong end of the nerfbat for obvious reasons.
Psionic Talent
Psionic Talent is a good feat to take when nothing jumps out at you. The second one is as good as an Extra Slot on a primary caster, and it's only up from there.
Multiclassing
My favorite multiclass for E6, regardless of whether the Ardent trick is allowed, is Wilder 3/Ardent 2/X 1. This is mostly for Wild Surge 2. With Quick Recovery and Enervation Resistance, enervation costs only 1PP and a move action. The save can be pretty easy, too, thanks to multiclassing good will saves: with Wis 18, Cha 11, and nothing else, you pass on a 3. A 10% chance to lose 1PP and a move action, and a 1% chance of losing the standard and swift as well, adds up to a very safe Surge.
This build has the max augmentation capacity in E6. You can get 6PP Touch of Health that's comparable to CSW, a 1PP Touch of Health comparable to CLW, powerful astral constructs, high-damage blasts, the works.
The X level can be basically whatever you want, mindful of XP penalties. Another Ardent level (for PP, a power, and BAB) is nice, as is a level of Anarchic Initiate (PP, a power, and more power damage). The Wilder level (for PP, BAB, a lv2 power, and euphoria) works well, but it does increase your enervation cost. You can also cherry-pick anything you want for the concept.
