open-ended question with tons of possible answers
I agree with buying a car now to learn and upgrade when you feel you've out grown or understand what type of dune car you want
find a name brand car, some solid names go back to 2000ish and OG builders way back to the 70s
Funco, racer, tatum, alumicraft, SU, SCU, joefab sand limo, desert dynamics, sand cars.net, toys for big boys, Mosebuilt, raceco, foddrils, prowlers, and on and on, but who's still in business or what parts used on the build are still available
A-Arm versus Leading Arm front suspension
single shock, dual shock, bypass shocks
transmission VW type 1 002 091 094, mendeola e-box 2D S4 S4D S5, albins, fortin
fuel type pump gas, race gas, e85
pedals, hubs and brakes = CNC, wilwood, tatum, gearone, grey area
there is a lot to learn on differences and why one versus the other is a good/better choice