I get that 1-17 or w/e is just free for all, but after that, Is their cookie cutter builds? or Does it just vary on what you want
Just about every build, for every class, contains Backstep + Backstep cancel, and Quick Rebound. I think the only class that doesn't need Backstep is the Monk, since they get a superior version (called Sway) at level 30. I can't imagine going from 18 - 30 without BS+Cancel though, so I got it on my Monk. It's only 100 points(And I have plenty of points left over in my build, especially since all Priest subclasses are basically incomplete at the moment, and missing a ton of skills).
Easiest thing to do I think, is to get all of your skills that are prerequisites for higher level skills, then start raising the skills that you like using.
The only skills that have invincibility frames, as far as I know, are grab skills. Grapplers get a ton of them, while most other classes get 1.