Before Meteor is the soundtrack prior to A Realm Reborn and has some of the same tracks as A Realm Reborn and the music from Before Meteor is sprinkled throughout the other soundtracks. But, if you want to start from the OG, then it's completely fine.
Honestly, there some good and some bad in Before Meteor (Nemesis is on my favorite boss themes / Uematsu songs ever), but A Realm Reborn really goes full throttle.
Yeah, it's been ok so far, I'll probably just jump to ARR again since I was enjoying it a bit more.