That alot of my card magic rely on gimmicks and I am wondering where to learn some more advanced sleights. Books are my preferred method of learning (because I am broke) if it matters.
By Forces Unseen is a book praised for its originatlity and difficulty...only problem for you is its a bit expensive (only available in hardcover I beleive).
Depends what you mean by "more" advanced - BFU is "VERY" advanced, very very very hard, so get it if you're very good and still want a challenge. As far as sleights go, The Paper Engine is a very commonly recommended book, but has many sleights I use. Otherwise, perhaps look into some Marlo stuff, he's got an array of sleights...
if i were you i would go for d+M's trilogy ,you will learn many tricks ,some of which get great reactions (e.g fatal) and many different sleights: palming techniques,many controls, a few double lifts from the center of the deck etc.