id go either an HPI RS4 RTR for about 299, which is ready to go. just need fuel, fuel bottle, glow stick, etc.
or my personal recomendation (sp?) would be a tmaxx. it all depends on budget. if there is no budget, than a monster GT, by team associated, or a losi super truck is a good substitute.
but if youre completely new to nitro id stick with the tmaxx. is a pretty capable truck out of the boxx (sorry couldnt resist) and its newbie friendly
if youre looking for somthing 4x4 and fast there are a ton of 4x4 1/8th scale that can be had for a bit more money, by kyosho, OFNA, mugen, or the like.
but for dunes and alot of sand, i think id be like a kid in a candy store with a traxxas t-maxx and a set of dirt hawgs or paddles on
unless you arent new to nitro at all, then it comes down to budget