1. Motor Saver Air Filter
2. Fuel filter (I like Sullivan in-line because u can see inside of it)
3. Failsafe and/or Throttle return spring
4. 5 Cell Rechargeable battery pack
5. Better steering servo if you can swing it
Always run good fuel, I suggest Odonnle 20%.
Invest in a decent glo ignitor too some time soon. I use a Hobbico 1.5 hobby cell with the glo plug connector/clip. This will allow you better starts and not draw from your battery that you will need more-so for getting the EZ-Start motor spinning and spinning and spinning.
Hope this helps.
After you get settled in and running you will prob want to do some other upgrades. When you get to that point I will give you some more ideas. Like RPM A Arms, Lunnsford Titanium hingepins and turnbuckles, Dynamite/MIP CVD's, RPM Bumpers, Alum ladder braces, servo cover, ProLine servo saver/steering kit, big bore shocks.... and on and on........