I have Sterne but I'm an F2P player and I'm focusing on Frederika instead. Would it be nice to have Gaffgarion on the team? since it's easier to farm him now
Sterne is definitely better but you already missed his banner might come back but not so soon. If you haven't awaken 3 your stern, might focus on gaf and pick sterne up later.
The hell are you saying? Sterne isn't limited, his banner doesn't matter. He can keep farming Sterne's shards via his hard quest.
The better advice is to pick one UR to focus on first if you're F2P because of a lack of rainbow spheres. If you're focusing on Frederika (who is a better option than Sterne), then Gaff is a great alternative to Sterne. So yes, go Gaff if you must.