Upgrade t110ii or not?

Good afternoon everyone,
I’ve been handed a t110ii (first time I’ve ever had a server) and have finally managed to install unraid on it - mostly using it for plex server.
I’ve built a few computers before but have zero experience with servers and it’s a step learning curve.
My poweredge works with plex but it’s struggling and I wanted some advice on whether it’s worth trying to upgrade (CPU/ ram can take an additional 16gb, or GPU) or whether, ultimately, I’d be throwing money away and instead, should look to build a server from scratch.
The key point here is budget. My wife already thinks I spend too much on my tech ‘hobbies’ so I will need to keep the spend down to a couple of hundred £ max (but could update little by little over time without anyone being any the wiser!).
So, does anyone have a suggestion on this? Is the poweredge t110ii with trying to upgrade (to run plex on unraid) or bite the bullet and try to put something together myself (and again, any suggestions for this option greatly appreciated).