For now I have only seen one stable was of earning gems and that's through dailies and weeklys which per week total is 1000 gems. I expect the game to be as friendly with gems like destiny child (same devs) which gives alot of gems sources but nikke isn't as friendly in that aspect. With pulls costing more than destiny childs 2700 gems for a multi ,while nikke costs 3000 gems. The 300 gem gap isnt the problem. It is the difference in potential gems.
(This is dailies only because destiny child has other sources of free gems and if far more f2p friendly right now)
All the sources of gems in destiny child :
https://youtu.be/wX16TBfINfA
Unfortunately I haven't found a gem guide on nikke yet so I cant link it.
-Nikke gems per day:
100 gems (weekly adds 300 gems)
-Destiny child gems per day :
+400 gems (No weekly rewards)
Potential gems:
-Nikke 1 week= 1000 gems
-Destiny child 1 week = +3200 gems
(not including mission gems)
For destiny child it is above 400 because you get 50 gems per daily mission completed. The 400 is the gurenteed. The same as Nikke and it's 100 gems.
Gems are always scarce for f2p players but it shouldn't be to this point.
Basically the gem gain isnt good for long term. I hope they buff the gems because it's not enough to summon and save for banners you like as a f2p unless you heavily restrict yourself.
Everything about the game is amazing from waifus to gameplay mechanics but as a f2p I don't think that its gonna be fun. If new sources of gems are released then I will change my opinion but right now. The gems are lackluster.