Basically just do the MSQ for now, that'll be enough to get you to 2.0 stuff, and maybe even a level or two. You only need to be at level 50 to start out after completing the story so you don't need to worry about leveling for now. All the optional dungeons you only have to worry about if you want to unlock the High Level dungeon roloutte for when you are going for Law/any other reward it might give, and even then it isn't a big deal if you don't have it done till much later.