Questions about the game

Hello!

I just came back from the game, and well it's overwhelming the amount of content the game has! I left at Mastery Rank 15.

Basically, my questions are:

1. What should I do first? Should I do Eidolons first or the Quests?

2. What are the META weapons at the moment?

3. What frames are meta?

4. What are the best frames and weapons for Steel Path?