I have scratch built several tanks, though not a Rhino specifically. As you have surmised, the running gear is the primary problem. Hull panels are easy to make for the chunky
GW style designs, but track links and road wheels are more of a hassle. One way to get around this is incorporating pieces from toys or model kits to the design. For example, this tank which I built several years ago.
It uses spare tracks and rear sprockets taken from a kit of a Russian KV-2 that I built some time ago and incorporates a lot of other detail parts from elsewhere, such as the turret cupola, some tools and a few pieces of photoetch.
For practical advice, I suggest investing in a steel ruler and a good utility knife for cutting sheet styrene with (should work decently well up to about 1.5mm or so). When assembling things from flat panels, you want to get them cut as neatly and accurately as possible. A small carpenter's square or some other way to get clean 90-degree cuts is also a lifesaver.