In need of hobby.

Ok so yeah i'm in need of an inexpensive hobby that i can do on my own at any time of the day any where no matter what. I spend to much time just sitting around wasting time and really the only thing i can think of doing is read a manga but that becomes very expensive very quick since most manga cost about 5 dollars and you have to buy a whole series just to get the full effect and story of the series. Plus i am into heroclix and other card games but they require hundreds of dollars to be put out for pieces and a friend or 2 to play them with. also gaming has become very expensive since games cost more then 40 dollars at times and hard limited to at home play unless i have my ds with me. oragami is a thought but i would needs lots of square paper to carry with me and that becomes a bit space consuming but it is a possible outcome. i was thinking about getting a math book and just learning how to do more complex math problems and then having a math major or math teacher check them for me just so that i know that i'm doing them right, but at the moment i can't find any good advanced mathmatics books that give lots of equations and examples so that i can do that. if i could get my hands on a school math book like a calculus book that would be great but for now i'm looking into something else that i can do on whenever, wherever, forever, and be able to do it alone. If you have any thoughts comment me and please me them logical and not comical.