350 now, I added 50 yesterday. That should last me for a month or two, unless they do another Over The Rainbow gacha at half the price it is now. But I'm really more in need of equipment storage, 300 (that's the current cap) is far from enough to dress up all my girls.
If anything, maximum jewelry storage should be at least 3 times the amount of available girls. At least, I figure they do want us to actually use those flower gems and thus have a reason to gather or even buy them?