Try to give your best answer, and I would appreciate a ridiculously long and in-depth answer too. I live in Mississauga, Canada, and I would like to know every part I would require (give actual examples if you can) and where I can buy them. (Not online, but a real shop in Mississauga) If you can, please list combinations of parts with actual names. Thank you very much!

I was thinking of building my own pc, but im not 100% sure on all the parts i would need. So if you could list the parts i would need, and a resonable place to get them from. Also i was looking at spending around £400 with or without peripherals.