I have some money what is the best way to improve quality and performance of my yamaha TT-R 125?

Question

how do i keep the bike in the best shape possable

Answer 1

seriously? if you are thinking more than a pipe and maybe a gear change, you should maybe consider going to a larger bike. If you start changing pistons, boring it out etc, you are going to run into a lot of reliability issues.

Answer 2

get a big bore kit...

could also change the gearing if you specificly want just more speed or more acceleration....  

Answer 3

intake and exhaust pipes, then jetting. will need to dyno it. see your local dealer