Perhaps I should explain the associated 'why's too. The booklist is notably limited and GP and exp gain are very fast making one-shot items far more valuable (MiC isn't on the list, unfortunately, and neither is A&E Guide - didn't think this is relevant since Potions are made of spells). First level is generally 2-3 combats and we get wealth by WBL, so effectively on level 2, we have 1000 GP and perhaps 4-5 fights before level 3. That means it's easily doable to spend 200 on 50gp level 1 consumables for each fight without severely hampering oneself. Since permanent items of the same effects tend to cost far more than there are probably ever going to be fights, one-shots are really handy, especially on level 1 (the said Psionic Tattoos of Expansion). Also, it gives me the option to size up the opposition and decide how strong effects I need to win.
Basically, I know Potions aren't really good in normal gameplay, but this is anything but and potions really tend to be worth using in this system (not healing, of course; healing potions are worthless - I'm just not gonna heal at all since Healing Belt ain't available, I won't have UMD with 6 Charisma crossclass UMD and Out Of Combat-healing is free). I'm just looking for the potions that give me most bang for the buck; Expansion is awesome since I'll be doing Grappling (yet again another thing that's much more valuable in 1v1 low level setting than normal campaigns) and being large is very useful for that.
Available books with spells:
Core 3.5, CA, SpC, CD, Races of Eberron, Manual of the Planes 3.5 Update, Deities & Demigods 3.5 Update, Savage Species 3.5 Update, Libris Mortis
