Um, this isn't related to FGs. The 500 points quest unlocks FGs for you, but in no other way is related.
But, anyways, people say you should get Eternity because it's incredibly powerful and not used by any elder (so you can't get them Elder farming).
Dem Ninjas, stealing ur posts.
But, lucky spins do give you everything but Eternity or Trident. Pick what you want to use most though. Pulverizer and Lobotomizer are pretty strong too.