Hi Emara, I'm a professional editor, and I predominantly use Premiere Pro, but depending on the clients or production companies I do the work for, I also work on Da Vinci, Edius Pro, and I'm also currently learning Avid. I think if you already have Premiere Pro installed, learn that, it's a powerful program, especially if you are using other Adobe programs, and it's user friendly too.
I can't comment on making FMVs though as I don't do those. When it comes to music, look for royalty free music. There are a lot of channels on YouTube and SoundCloud that offer these, otherwise there are a lot of subscription services for royalty free music, but if you're doing this for fun and personal projects instead of making a living out of editing, I think you're better off looking for free ones on YouTube or Soundclouds, just make sure you follow the creators' terms and conditions for using their work. For editing tutorials, there are a lot out there, but I find Premiere Gal on YouTube is quite good, and she covers a wide range of topics: https://www.youtube.com/c/PremiereGal/videos. If you want to learn more about editing, I'd suggest hitting up blogs on sites like Premiumbeat, NoFilmSchool, Rocketstock and the like.
All the best :)