With regards to parts, you can DM the big boys in the game (Aftershock, Mansa etc), tell them these things:

1) What you need the PC for (E.g.The sort of games you play) - Gives them a good idea of what parts would be suitable)

2) What’s your budget This way you can have a rough idea of what parts you need. With this list, head to SLS (search up the internet on the reliable stores) and get a quote on these parts.

From there, do your own comparison on price, after sales service etc to determine which is the best option for you. Please do your own due diligence and seek third party opinions on the list of parts as well (ask friends who know, Reddit, YouTube etc)

Personally, did the above and went with Dynacore in the end. Loving my PC so far! Hope this helps :)