Thought of it...
The books I know I am going to buy:
PHB, DMG, MM1, SpC
The ones I think I'll buy:
CArc, CMage, UA (since I found all of them for less than 10$, 2.99$ in the case of CArc)
And the ones I only can take one of because of money limit:
PHB 2, CAdv, CScou, Dungeonscape, anything awesome suggested in this thread...
What of those 4 is best, BTW?