Buying stuffs which you don't really need for now specially if you're new to the hobby/racin'. Some guys buy alot of hop-ups hoping it'll make em' go fast around the track. Just to realize they are fast,,,,"across" the track that is.

Buying only the essentials will keep you from getting frustrated and eventually quit. Also it'll save you alot of cash, too! for future expenses like parts. tires and stuffs. If you're new Just run what you brung,, and time will come you will be one of the fast guys on the track,, that's a sure thing!