If you’re trying to keep it simple, get 2 Pz IVs, a Pz IVD, paint it grey, for early to mid war and a PzIVG or H and paint it dark yellow, red brown and olive green cammo for mid to late.
This!
The early, short barrelled, version covers Poland, the Fall of France and the early parts of the North Africa campaign.
The later, long barrelled, version covers the Eastern Front, later North Africa, Italy, D-Day and North West Europe.
Even early war the PzIII is beginning to show it's age and by the time Kursk is over the PzIII is pretty much relegated to being a training tank or they are being retrofitted as assault guns (by both the Germans and the Russians).