Welcome - many good people are on this forum and willing to offer advice.
I have been doing this more than 60 years and still am unsure in certain areas, so my first advice is - take your time. The world can be overwhelming so peck along at a learn-as-you-go pace.
That said, you might want to pick just 2 or 3 countries to start and focus on and see what works - the use of stock pages, stockbooks, albums, self-made album pages, etc.
First to address, though, is to make sure you have a decent catalog for you areas. Plus regular supplies - tongs, magnifier, per gauge, glassines and stock pages.
Good luck.
p.s. Be sure to make time to get to the Colopex show May 31-June 1 in Columbus. You will meet a lot of good and helpful collectors there -
https://www.colopex.com/colopex