Diagnostic Tools

Hi! Anyone around who could give advice on diagnostic tools that would work well on a 2000 civic vti? i'm thinking of investing on one, but i'd also want to be able to use it on other vehicles as well. what are the good ones that are available on the market? and what about the price range? additional information about diagnostic tools would also be appreciated (e.g. what are the kinds that you connect to a computer; how to use them; etc.)... i'm kinda new to this thing. Thanks a lot!