Welcome aboard Fruitymaths.
What is your intended uses for a computer? That will narrow it down a bit. There's different builds that's catered to specific uses.
I build my own so for my purposes I built my system for normal browsing, a little gaming and watching videos. Since I intend to keep it for years I've built mine with a business grade motherboard, an enterprise hard drive, 8 gigs of memory and a decent video card. Of course the most important, a good power supply.
Ask away about whatever you need and don't be a stranger.