Welcome. I have to assume it's this particular version:

http://www2.giant-bicycles.com/en-gb...llections_id=3

First thing I'd probably look at changing is ditching the Suntour fork for something like a Marz Dirt Jumper or similar. Next up would be brakes: not so much an issue if you were just flowing the DJs or skate park; but if you're actually going to start racing 4X, you're going to want something you can depend on.

From there, I'd say just ride the thing until stuff starts giving out and then replace it. The Suntour cranks/BB will eventually give it up, as will probably the wheels. But just take it a piece at a time and spread the pain.