Welcome!
How familiar are you with keyboard switches? Have you ever used MX-Cherry switches, Gateron, Zealios, etc?
If you're not too familiar, it'll be hard to know what kind of switches you'll end up really liking. Not sure if there are any local keyboard meetings in your city, but that would be a good place to try some keyboards.
As for building, I'd start with something simple like
https://kbdfans.com/ They sell full kits and separate parts, but you'll have to do your research to see which pieces are compatible with one another.
This will likely be only your first keyboard of more to come, so no need to try to build the
perfect keyboard on your first shot.