In this first post I will talk in general about pcs and about components.
Ok, let's start, first thing: you MUSTN'T buy a prebuilded pc, in the 99% of the cases a prebuilded pc isn't worth what it costs; you have to buy the different components and then build it by yourself or paying someone (or not paying if he's a friend lol) to assemble it, but you have to buy the components by yourself (usually technicians are bad in this topic).
If you want to buy a new pc, you have to inform yourself from internet, youtube, and there are many groups on telegram who talks about this; to recognize who says a correct thing, and who doesn't you can easily compare the different informations between youtube, the web and others. For example, here there are some good pc talking about youtube channels (this is not sponsorized): https://www.youtube.com/user/wiltshire12345 - https://www.youtube.com/user/AwesomeSauceNews - https://www.youtube.com/user/Tom5TomEntertainment - https://www.youtube.com/user/eteknix - https://www.youtube.com/user/ThanatoSVideogames (this last one is italian, but I think you have subtitles, if you haven't then sorry), and this is a video where them and others explain why another video is full of disinformation: https://www.youtube.com/channel/UCy7gWknV1ZzuEDfhNsudVxw .
Ok, now I gave you some informations about where to know this world, but you have a few more things to know: you should always prepare a pc configuration (what pc parts to buy) when you are buying it, or in a range of maximum 3 days before you're buying it. Buying a pc by components but not everything together sometimes it's a good idea, it depends on you, if you can buy it right now, you have enough money and things like that; this because the market change's very fast, I've seen a cpu (amd r5 3600) going from 170 to 200+ in like two weeks. Next thing, when and if you're asking the configuration to someone (for example in a telegram group) you should always list this things: budget, usage of the pc, if you have preferences on the case (with rgbs or without, black white and things like this) and if you stream or record for youtube which game do you play, on with resolutions. There is people that think to build a gaming pc (in this blog I won't talk only about gaming pcs) it requires minimum 1000/1300€, this is fake, just ignore them, on youtube there's people that created a gaming pc with 200€.
I think I've said everything for this post, just informate on internet, compare the informations, watch youtube videos and these things... if you have anything to ask me just ask (@Fillemooon on telegram, Fillemooon#5066 on discord, @itz.fillemooon on instagram), be careful about disinformation and have a good day :)