Hi Stuart,
That looks pretty good to me. I don't know much about the M36 but from what I can see you have done a good job on the kit.
I don't know what sort of tracks trhe kit has, but they look like they may be pads in which case I'd add a coat of grey to the stowed ones on the front and some gun metal./metalic to the connectors.
The overall effect looks good, well used but not overdone. Depending upon the final setting for the vehicle you could add some light/brick dust and if it's in a field some mud to the tracks and under hull.
That's an excellent first build IMHO.
Cheers and thanks for sharing.
Al