You can have all the fancy stuff and it won't mean diddly if you don't practice. That's the #1 thing that will make you competitive; that and tires. An expensive setup station will not make you competitive. Especially in off-road where things get banged up pretty bad.

The back-up car is a nice idea in theory, but I've seen guys try to do that here and the backup gets canibalized for parts. Some guys have a "practice" buggy and a "race" buggy, but the maintenance becomes too much and usually, they can't seem to get both of them handling exactly the same. An extra car is a good idea if only for the fact that you have an extra of everything.

One thing that I've seen some guys do is get an entire radio tray together complete with servos, receiver and a receiver pack. It's easier to swap out a radio tray than to swap out a single servo. I would also go to the track and see what the fast guys are running for tires. Generally, there's just a few popular styles for various track conditions. No sense in spending money on tires you may never use.