Hi mroakley, thank you for posting.
Naturally every player will need to focus their study on different areas. Pro will likely study one particular spot at a time, such as 4-bet pots out of position, or perhaps if they fell they were massively outplayed by someone in their last session, they will look to see what that play was doing differently compared to them and see if it is something they can or should incorporate into their game.
Beginners should start studying the fundamentals, simply by reading a book or a course such as CardsChat's own 30 day course -
https://www.cardschat.com/become-a-winning-poker-player/. There is so much to learn that will have a significant and immediate improvement on your game and is relatively inexpensive (or free in the cash of the 30 day course). I would also suggest checking out PokerCoaching.com and RaiseYourEdge. They both have some free content and much more on YouTube. This will help you to build a basic fundamentally sound game that you can then begin to expand on.
If you consider yourself an intermediate, you should start to look at leaks in your game. Perhaps you tend to lose a lot of money from the blinds, or when you get check-raised on the flop. You may be defending your blinds too wide, or maybe not enough, or you could be continuation betting too much when the board connects better with your opponents pre-flop calling range than your pre-flop raising range.
Hope this helps. Good luck in your games.