Master Basics 1 or move on to Basics 2?
Is it better to spend the time mastering one level before moving onto the next one when it becomes accessible?
If you look carefully Duolingo will recommend which unit you should do by highlighting the button. Duolingo recommends the strategy to jump around which I myself would recommend. I find that if you try mastering a unit before moving on, you are not really learning but memorizing the answers.
My personal strategy has been to move on as soon as I unlock the next level, and if I feel like I'm starting to get stuck, I go back and get my mastery in those modules by translating sentences. It seems to be working for me pretty well so far.