I was kinda hoping someone else would chime in on a budget build, as im not very good at it but we'll give it a try.
https://uk.pcpartpicker.com/list/mQNKK3
AMD Ryzen 3 3100, its slightly better then the 4770 you have but opens the door to way better upgrades on CPU's
MSI B450 Tomahawk Max, can use the R3 3100 but will also accept the new 5000 Series once stock becomes available
G.skill Aegis 16GB 3000Mhz CL16 middle ground speed and enough to keep any game happy.
£286.94 so slightly above budget but you might be able to find in store sales, even ebay for a secondhand cpu if you can find one cheap.