Ari,
Bill is making good points. Racers often are looking to buy speed (motor, tires, chassis, etc, etc) when in reality, we should be looking in the mirror. The driver makes the difference more than anything else. This is a post from another thread:
Driving is worth seconds.
Chassis tuning is worth tenths.
Engine is worth hundredths.
Prioritize accordingly.
However, with that said, Your equipment does need to be in good condition. If your motor has more than 12 hours it is likely in need of at least a top-end rebuild. Will you suddenly have more power and speed…probably not. You mentioned you are new to racing, in my experience with my son and I racing KA as well as seeing new karters at the track, it can take seasons before you are on pace with the fastest guys at your track. Some karters have more talent or other experience but a racing kart is its own animal and it takes time to master it…if ever!