I'm a fairly new tanker myself. My thoughts:

Heng Long makes some nice, cheap, all-plastic tanks. They generally have plastic tracks and plastic-geared gearboxes with slip clutches in them to prevent stripping gear teeth. On light tanks, like the Sherman, this works pretty well, but on heavier tanks, like the Jagdpanther, you will find the clutch slipping under many common loadings, like running in grass or up a hill.

It's tempting to buy the cheap ones with an eye towards upgrading, but you will find that you can easily sink lots of money into them that way.

I like the 2.4 Ghz tanks that give you audio volume control and smoke on/off from the remote.

If you buy a Heng Long tank with metal tracks and metal drive/idler wheels, it will probably come with a metal-geared transmission. Sadly the pot-metal gears wear out quickly, so while you save buying the tank with its metal upgrade already you will want a steel-geared transmission from Imex shortly.

I suspect it's cheaper to buy a "loaded" tank from the get-go than do the upgrades yourself. But, if you're like me and you have to buy it "one piece at a time" to get past the Chief Financial Officer then you can go the upgrade route.

Steve