Weeellllll, the easy answer is to look
here. The thing that makes it difficult is just what you mentioned, terrain and skill. Weight is easy
My self, I sprung for my weight and then had it revalved for my terrain (race mostly open desert) and skill (open pro). What this ment was that I needed to handle the tight and twisty Hare -n- Hound stuff with the agility of a billy goat, and still be able to soak up a G-Out @ 100mph +
Try the springs first
Oh and don't forget that oil level and viscosity also affect suspension