There is an Action Bar at bottom of the User interface. Each class starts with some skills. Every few levels, you will unlock new skills specific to your character class, these can be learned from your Class trainer. You will be introduced to one of these NPCs during one of the first few quests you complete in your starting zone, but they can also be found in many towns and each of your Faction's cities.
Where to get materials and reagents you may ask? Buy for cheap off farmers in bulk or track Auction House lots. Get in touch with most big sellers. Communication is important here, send a whisper or write them a letter. It would be good for both of you to establish business relationships. Constant suppliers and buyers is convenient for both parties to save the time and effort.
Only really to expand on Gráinne's comment as regards the 'collecting' and 'roster development' sections - which are, as said 'distinct' although they are intrinsically linked - I would like to point you in the direction of the in-game Achievements > Battle Pets > Collect tab. There are a series of achievements called Raiding With Leashes, pretty much all of which can be completed via the auction house - if you have the gold/inclination - or by completing old raids.
Unlocking the Lightforged will require you to complete the aforementioned Argus storylines and earn the “You Are Now Prepared” achievement. In addition, you’ll have to earn Exalted status with the Army of Light. As with the Argussian Reach, this one could take a couple of weeks, as it is time-gated. However, the main story quests should help you at least reach Friendly status with the Army of Light.
Another way to make gold. This option works well at level 60 when you have some good gear already. Obviously, you should have some gold ready to buy reagents. Be ready for expenses up to 225 skill points in any profession: items below that are not worth much. You will get first income after 225 skill points in Leatherworking, Blacksmithing, Alchemy or Tailoring. Unfortunately, Engineering and Enchanting will still require some investments. The only way to make gold with enchanting is disenchanting skill (we talked about it).