I just came back to learning Spanish and now see that each skill has 5 levels. Should I do all 5 levels in a skill before going to the next skill or should I finish level 2 in EVERY skill before going back to the beginning and working on level 3?
Your question is a bit confusing, but I would start back at the beginning. Complete everything in chronological order, is my tip. Sorry if this doesn't answer your question, good luck!
You will perish from boredom if you try to get to level 5 of each skill before moving on to the next skill. But doing one level at a time is not necessary either. After everything is at level 1 or higher, it's fine to just follow your interests, doing some "Practice" (what used to be called "Strengthen Skills") to counteract decay.