Lets say I don't care about boot times and want to be cheap. Could I buy a smaller ssd and just load the games to it and not the os? Would I still get gaming benifits for games that it helps, even while neglecting the os?
Pretty much the only benefit you'd see would be decreased loading times. If loading times are the bane of your existence, then an SSD would be right for you. However you'd lose a lot of the inherent overall speed increase by not putting your OS on it (unless you game more than you do anything else).
THE only benifit you will see is Loading the game, and loading "map" during play. An SSD will NOT improve FPS, it can ONLY improve reads/writes to and from the SSD. If Game loads a lot of large files while playing the game. it will improve the performance during these load time, IE if you see a decrease in FPS while the Game goes out and loads a file, then speeds up after file is loaded - YES the SSD will improve this. Decrease in initial load of game (starting it), yes will improve - A BIGGY, absolutely Not as this has NO effect in itself on game play.