Welcome to the hobby.
It depends on what your preferences are, as to what recommendation to make. If you are a beginner are you concerned with detail, accuracy, the cost, etc?
You chose well with Tamiya the first time around. Whilst older kits and not as detailed, they are generally reasonably priced and have a name for quality and fit.
If you want fewer parts, good fit, and a tank that looks like a tank, try Tamiya's Panzer IV Ausf D. It is a very old mould so, if you want to up the ante a bit, Tamiya's Panzer 3 Ausf N may be a better option. More recent and it does come with an aluminium barrel and a little photo etch if you want to try your hand at that.
Dragon's Panzer 3 Ausf J may also be something to consider.
Dragon has also partnered with Platz to produce the IV D in a "fewer parts, lesser details, lesser (slightly)cost' product too. Their earlier IV kits have a LOT of parts, and can be a bit finicky to build, but again, if you want to stretch yourself, you can try them - any Panzer IV Ausf A, B, C, D or F1 would fit your grey colour bill.
I suggest you look at a few reviews online and use them as a guidehttp://www.perthmilitarymodelling.com/reviews/vehicles/tamiya/tam35290.html