The main thing to get right is the tyres, if you're on dry astro you want Schumacher Yellow minispikes all round. Not running the kit Proline Holeshot and ribs (which are intended for clay tracks) will be most of your problems sorted
Whether you need to go mid-motor or not and changing things like ESC's/motors depends on if you're getting the most out of the car as it is now. Generally for newer racers it's more important to get the basics sorted (like steering trim ect), then concentrate on getting round without errors. Once you have the car doing what you tell it and can get round with no more than a couple of mistakes per run, then it's time to start going faster
Rich