The baja lacks in power so the best upgrade would be a exhaust pipe. The cheapest one on the market would probably be a x-can which would give you lots of low end power. Another cheap upgrade would be to get some outerwears. The stock parts on a baja will last you a long time, It really depends on how you drive. Only thing you might wanna watch out for is the rear tires, they will wear out in only a few runs if you run your baja on asphalt.

-Pete