Also, I think being constrained by a budget is nice rather than frustrating. Compromises, situational things to take into consideration - simply more interesting. Where are the price/performance knees? What are the recent or upcoming shifts in technology? What can be replaced or extended easily (such as RAM) vs. what is more costly or has domino effects?
From where I stand, you made a good job within your constraints. And since there are constraints an upgrade somewhere would have to be paired with a downgrade somewhere else.
Unless you go VR, or a new generation of consoles defines a new baseline for game development, there will be little need to do much of anything with that build.
That's how I feel too. Dunno if you ever were constrained by a budget, but you need to consider balance. +24€ I'd have a Ryzen 1600, +40€ the GPU's ram would go from 4GB to 8GB -although I find the first change to be the better deal-, etc. But that money could be well spent on a SSD...
When I got my first PC I wasn't on a budget, I spent like 3000$ on it, a top notch PC for its time. 1MB of RAM cost 30€, so by those metrics a modern PC with 8GB of RAM and a similar price would cost more than 200000€. It ended up being a great PC, but I didn't have a 3D accelerator, which I bought later, a Monster 3D graphics card --expensive but well worth it.
However it was quite disheartening to discover that games and programs weren't running that well two years later, in 1997. I remember Sega Worlwide Soccer and other games of the time running close to single digits framerates. I waited and upgraded my old Pentium 100 to a Celeron 400MHz in 1999, along with 256MB of RAM. This one lasted a longer while and was my PC for some years, a SoundBlaster Live!, a Voodoo 3 PCI and a Matrox G400 AGP (was on a budget with this one, there was the MAX version of it that was slightly better but much more expensive) card gave very good results at the time.
The Matrox G400 was the first GPU with environment mapped bump mapping, afaik, and was bundled with a game featuring it. It was also a true 32 bits card, contrary to the 16 bits Voodoo 3. The Voodoo 3 performed almost 3 times better with Glide, while the Matrox was quite good at Direct3d but framerate was much slower.
In that sense, there is a lesson to learn from DF articles and stuff like that. I am not a particular big fan of just getting the most expensive CPU and GPU, memory of the market and using that for years because there are other considerations.
If a CPU performs particularly well and its coupled with an also excellent and well balanced GPU, with an excellent ratio between power and thermals, then that could be a winner. If you get the fastest CPU and GPU, you are going to enjoy a great experience from years to come, but more efficient solutions will be available some time afterwards.
If you look at the economy of each part and its impact, £50 more CPU or RAM or GPU won't net you much difference above the bottom of the barrel, but £50 of SSD can reduce operating lag to a fraction. All that time saved over the life of operation is well worth it. I get by okay on an older 120 GB SSD. So if a choice between £200 of CPU and GPU or £150 of CPU and GPU and SSD, I'd pick the latter every time.
Next upgrade is going to be a SSD and Vega, hopefully -depends on thermals and power consumption (don't want to switch my 450W power supply any time soon-.
Despite not having a SSD yet, after getting used to my laptop CPU consuming 6W of energy and its very slow operation overall, this thing feels like it is flying to me, despite the fact that I didn't use it intensely yet in any way.
While I am not into video editing -though the graphics card comes with some good MSI and AMD utilities to record video in real time with little impact-, a mechanical HD having to seek small files and constantly moving the head around to find them...there is no way it can match a SSD in productivity tasks.