No worries, we've all been where you are.

No, unfortunately, combining points/miles from one FF program to another is generally not possible. (There are some third party companies that will do so, but they extract very high "commissions" in the process, making the whole transaction uneconomic.)

To get your feet wet, start by reading the sticky threads in this and other forums. What you need to do is look at your flying (and credit card, if applicable) patterns and preferences, then pick a program that works best for you. While miles/points aren't interchangeable, you can usually use one airline's miles/points for redemptions on that airline's partners - either in the same alliance or in some cases unaligned partners - or for non-flying activities. Each airline has different "earning and burning" characteristics - how miles/points are earned and used, and you'll need to investigate these carefully, as the differences can be significant and expensive (or beneficial) to you depending on your choices.

One important thing to note is that miles/points earning and redemption are only a part of the whole FF business. A big factor in choosing your plan preferences is whether you'd fly enough with your chosen airline(s) in order to reach elite frequent flyer status. With elite status comes various perks - access to lounges, expedited passage through airports, seat selections, upgrades, baggage allowances, etc. - that can be as important if not more important to frequent travelers. So those factors also need to be understood as you make your choices.

It involves homework and research, but the rewards can be very significant, well worth the effort. (Or so many of us think. Of course we can be both delusional and exhibit OCD symptoms in this regard. Welcome to the madhouse.)