Poochie...

I think you are on the right track so far.

Pointers from me:

Try looking around google for some hi res pictures of deserts, reference is always king!

Skys in the desert vary alot, its not unheard of to have a cloudless sky but maybe some cloud will give it some depth. Perhaps make the blue a bit more bluer and not so cyan.

Add debris and stuff around the place, if its post apocalyptic

Light sources, remember the lower the sun, the longer the shadows. Id higher the light a little more. perhaps stick in another light without shadows but with a little yellow/orange color to give the feeling of bounced light, unless you want FG or GI in MR, but the renders will take longer for sure.

The sand could do with some bump, so in Photoshop create a tileable texture with just noise and repeat the texture on the bump channel throughout.

Why dont you have the droid emit a smoke/cloud particle instead of worrying too much about tracks in the sand.

On a last note, you could be making life difficult for yourself by asking too much, look at the bigger picture instead, concentrate on the animation side of things first then go in and fix the other stuff later

But have fun with it, dont sweat it....

Best
Jay