You have a pretty nice beginner setup to start with. I was in a pretty similar situation before i gradually lost my mind and spent a fortune.
The problem with identifying possible upgrades might be though, that with your current background, it is probably quite hard to actually know, what spending more money on individual components brings you and feels like.
- PC: if you really plan to go much beyond what you have now, switching to a PC is hardly avoidable. You will have endless opportunities in terms of games (race, flight etc.) and peripherals. This is a major upgrade in terms of cash (initial, upgrades over time) and dedication though.
- Rig: the basis for most advanced rigs is some kind of solid frame, aluminium extrusion based, steel or whatever. Cost is probably from a couple of hundred EUR and up. You buy the flexibility to mount stuff you previously couldnt and change ergonomics. It most often offers the possibility for better seating position (think differences between GT-cars, formula etc.).
- Seat: Along with that comes the ability to mount car, sports car or bucket seats. That will cost extra too of course, my bucket e.g. was 650 EUR on its own. I started with a 200EUR used RECARO seat...big improvement for ergonomics.
- Wheelbase/Pedals: For stronger bases and loadcell pedals a sturdy rig is not optional. I initially used a Fanatec CSW2.5 base and V3 pedals with my Playseat challenge, but there was flex everywhere. I wouldnt think about any direct-drive wheels on that. Load-cell pedals would enourmously improve both immersion and control, as braking is proportional to the pressure on the pedal, not the position of the pedal. Number one upgrade in my opinion for improving your driving. DD wheelbases starting from a Fanatec CSL DD will set you back another 500EUR or more and you can/have to buy wheel rims for that. The variety is almost endless, but each rim costs money.
- Lots of other stuff
: shifters, tactile, motion, VR .........
I could now post a pic of my current rig and the bill that comes with that, but i dont think that would add much to the discussion
There was a lot of buy twice involved, as i could not imagine spending so much on a rig in the beginning.
If you really want some advice for a single, affordable upgrade that can be used with your existing stuff, i would probably look at loadcell pedals like the T-LCM from Thrustmaster. You should be able to get some solid improvement in terms of feel and driving technique out of that.