Of the books you have listed and given that you tend towards spellcasters I would probably pick up Complete Arcane. It will probably have the most useful items in it for you.
It seems for you Complete Arcane is the obvious choice; however, I voted for Complete Adventurer. I own them all, and this one had the most stuff that I could drop into my game right now, rather than having to work up things from the other books.
If you have Tome and Blood - then buy none of the above.
if not buy Complete Arcane
I dont have CAdv - its the oddball class combos that bug me.
especially prestige classes for them. All right 1 paladin/Rogue I can understand but and organization of them? But I really cant speak much about it, there may be useful bits I just havent seen. I have gone through the 2 others - they can be skipped.
I voted Complete Arcane, because you said you liked casters. For myself, that'd be a close second to Complete Adventurer, which seemed to ooze ideas when I read it.
Of the series, Complete Divine was the only weak one, but even that is worth having.