You might do better with videos than texts. Have you checked out Mathtv and Khan academy? You'll find a range of math videos, at a range of levels. I'd also check out Norman Wildberger. He's a professor in Australia who's made umpteen dozen math videos, some at the grad school level, others at the K-6 level. I suppose you could just breeze through a series until you find something that challenges you. The videos of his I've seen all include a handful of exercises.

As for texts, you could go on Amazon or Ebay and look for old copies you can buy cheap. It sounds like you might not need current editions.

If you can provide more exact info on just what you want to learn right now, that would help. In Algebra, do you understand the binomial theorem? My guess is you've at least heard of it. In Geometry, can you name the plane isometries? Have you heard of circle inversion or Feuerbach's theorem? I'm guessing not, in which you can look forward to a lot of enjoyment.