So - I used PCpartpicker and then searched for each of my parts online that fit my budget! Some were amazon, and some actually ended up coming for currys as they had an offer on at the time!
Generally i'd advise not getting a second hand graphics card anymore, as it'll almost certainly have been used for crypto. 3200mhz ram is more than enough too. Dont be lured into the super speedy stuff. You'll see very very very minimal FPS improvements and it just doesnt justify the extra cost. You'll want a decent m.2 drive, any of the samsung evo lot are really good.
There are tons and tons of guides and build guides on youtube to look at and they'll walk you through it. Building really isnt as hard as you may think it is! Any issues, just ping me on discord, but genuinely you'll be fine!