Personally, I've taken to doing Daily Hunts for exp. Each Tier 1 hunt set (1-3 mobs) gives equal exp to an NThan FATE with armoury bonus (around 21k exp), Tier 3s give 24-48k depending on the hunt. You can do these as many times a day as you want. Complete a set, go back and restock. The best part is, they all give those precious centurio seals that everyone fights over on A-Rank hunts. Before you know it, you will be full and spending them. They give 4-15 seals depending on tier, per hunt. It's very effective. Other than that, just do daily roulettes as well. You don't have to fate grind anywhere to level past 50.