you want the quad to be light.
get some good suspension: +2+1 A-Arms (Quicksand) , rear and front shocks w/Rezzys (Works,Elka), -2 Swingarm, +4 Axle, Steering Stabilizer, Steel Braided Bake Lines, new Rotors, Skid plates
As for the engine: an mx port job (Patriot Racing), pro design air filter (k&n,foam) , Modified head/Aftermarket head, Low end pipes (PTR mids, Fattys), Reeds, Trinity 2 in 1 carb
new tires, 2ply or 4 ply, maybe some kenda klaws. my list isnt really everything you need, but just an idea of what to get. its all about personal preference.