Presumably, you can do the same with Amber.
I'm saving the rest of my gems. I don't think I want Xiao. Honestly, I'm kinda waiting for some new 4-stars to show up. We still have a lot of representation left to go. Some more polearm users would be nice. Some DPS water users, for four-stars, we got, what, Xingqiu? More anemo characters too, as we only have Sucrose. I imagine they're waiting for the next region to dole out new ones, so all the banners we'll see until then will be repeat characters outside of the five-star.