How do I advance skills in Spanish? All skills are orange
Well, if all your skills are orange ("gold") and there are no more, you have done all the lessons in Spanish! Congrats if that's the case!
If you hover over your user name in the blue bar at the top then click on "Your Profile" it will bring up a screen that tells you your level and how many XP you need to get to the next level. You get the XP by strengthening skills or redoing lessons or you can get some by going through the stories in the Labs section if you haven't already. It seems that the higher you go, the more XP you need to move on to the next level. Frustrating when you're caught up on reviews, but that's the way it is.
Oddly, even after you've achieved the highest level and gilded the entire tree, you will keep getting new words. You just keep practicing.
And, yes, you will learn even more doing the reverse tree. I am doing both right now. There are some different words in the reverse tree. I thought I would zoom through it, but it's been slower than I thought.