As a beginner as well, the main upgrade you will need to have if you plan on running offroad and non-smooth surfaces, is a gearbox with some metal gears (even the zinc is better than the plastic). Plastic tracks are dirt cheap, but keep your tank light. Realism equals metal for tracks and such for decent "sag" effects, You'll want metal tracks and sprockets/idlers for that as well. One of the best I've seen is Taigen's KV-1 metal lower.

Heavier = higher levels of stress