I tend to go to bookstores and the local library and read/borrow manga rather than actually buy it *is cheap*. But if I find a series I really like, I'll buy the whole thing:

Chobits vol.1-8

*is undeniably all man*

I'm on the hunt for:

Angelic Layer
Tsubasa
Rurouni Kenshin

I also wanted Cowboy Bebop but I watched the anime and it's a bazillion times better (you just can't capture the beauty of Ed in text format)