Will this be overkill or otherwise not recommended for someone who is new and just starting to learn?
My goal is to have something I can grow into, but initially I'd like to host a few VMs, game servers, and a have place to store content. I'd also like to host a PLEX server in the future as well but might buy a separate piece of hardware for it specifically down the road. Thanks in advance for taking the time to help a newbie!
I think that for starters the R720 can be a good choice. It's cheap, parts are also cheap and it's a fully fledged rack server. It can have plenty of cores and ram to host lots of services to start learning.
The R720 is the end of the line for DDR3 based systems. Simply going to a R730 gets you DDR4 and newer iDRAC is better than old iDRAC. It also lets you use V3 and V4 Xeons and it is practically the same price. My local recycler isn't even bothering with 12gen Poweredges anymore.
In my country ( Italy) prices are quite different. The R,720 are cheap but newer equipment are pricier. Also for a starter I don't think there will be much of a difference between 12th and 13th generation. Of course if the price is close the newer is better.