The CPU upgrade depends on what you need to do for your system. If it's a workstation, editing or running virtual machines, I would lean more towards Ryzen for a higher core count. Ryzen works well on gaming, don't get me wrong, but I feel Ryzen shines when it's actually using all the cores it has, which, will be from the above examples -- someone feel free to correct me if I'm wrong, but a good portion of games only really utilise four cores or so.

If you were to upgrade to an i5, you could get something like an i5-4690/(k) -- which is still very relevant in 2018 if you're on a slight budget and can can't afford to upgrade to Coffee Lake/Ryzen with a brand new CPU, motherboard and RAM. If you have a budget that you are comfortable to spend on, you could upgrade your whole CPU, motherboard and of course RAM with either a Ryzen build or a Coffee Lake build.

At the end, if you go Ryzen or Coffee Lake, you will need a new motherboard, CPU and RAM. If you want to jump into an i5, the 4690 / 4690k would be a reasonable jump; however, prices on them seem to be a little higher than I remember when I got mine back in 2015, I spent around $260-ish on it and it seems now they're in the $300 area.

If you decide to do a full overhaul on your CPU, motherboard and RAM, knowing your PSU and exact case will help tremendously. I know your current motherboard is a Micro-ATX, but it needs to be known if you have a bigger case with Micro-ATX standoffs or a smaller case meant to fit the motherboard. That's just to make sure that any motherboard suggestions will fit your case.

Give us your budget, that will be a main factor for deciding what's best suited for you.

SHOTTYLEAN wrote Give us your budget, that will be a main factor for deciding what's best suited for you.

I dont really have a set budget, Just looking for the cheapest option. I was looking at i5's n seen around 150GBP.

I mean, we really can't help without more information.

You're running a pretty low resolution monitor and an aging GPU, appears to be either an R9 270 or 270x, maybe an R9 285? So, a monitor or GPU upgrade would be better than a CPU upgrade for some games. You also don't have an SSD. If you were just looking for a quick upgrade to make your system feel a little snappier, SSD is the way to go. Honestly, adding an SSD would be the first thing I'd do with this system, regardless of what I used it for.

For a CPU upgrade, you're looking at either Coffee Lake or Ryzen if you're buying new, which means at least $70 for a motherboard(up to $100), $100+ for RAM, and $200 for R5/i5. Instead of doing that, I'd grab a Haswell(Refresh) i5/i7 or Xeon, then use the remaining $200 for a nice 240GB SSD and a 1080p or 2560x1080 ultrawide monitor. Something like this;
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and here's a 4670k for $120;
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i5-4440, 4460, 4570, 4590, 4670(k), 4690(k) and Xeon E3-1220 V3 are all solid 4C/4T options that should cost between $100-125 used.
Alternatively, i7-4770(k), 4790(k) or Xeon E3-1230/1231 V3 for 4C/8T. Should be $160-170 for the locked i7 and Xeon's, but you'll probably be looking at closer to $200 for a 4790k since they're still pretty sought after.

We could help much easier/better if we knew your budget and currency, as well as what you use your system for exactly and where you feel it is lacking.