advice on choosing the first pc

hi guys, so i decided i wanted to build a pc for my bf, my plan was on getting in it for christmas but i had no idea of the prices lol anyway i started exploring this and also talked to snapchat ai for advice but some things i dont understand. the idea is to be a gaming pc, he likes cs:go and he wants forza and maybe minecraft so i dont know if it needs to be a really good pc or not. i know i need motherboard, cpu, memory and storage, video card (that i know it can be really expensive) and power supply, do i need anything more (besides monitor and keyboard)?

i want Micro-ATX Nox Infinity Zeta RGB because i liked it and its accessible.
i dont know the difference between Corsair Vengeance LPX (2x8GB) DDR4 2400MHz and DDR4 3200MHz, which one should i buy?
also dont know if i should buy a 500gb ssd or 1tb, probably the latter right?
for the rest i dont really know, im seeing so many things i dont know if its compatible or ifs its enough, and i want to be accessible, i dont really have a price range but yeah nothing too expensive.

if you could help me with suggestions i would really appreciate it also sorry if anything is spelled wrong.
thanks!!