Well, looking at your scorecard (hooray), I see you still have two bosses to find and defeat - but you'll need more of those gems to do it...!

Luminous Tower A is paradoxically a lot easier if you take your time - find the route that feeds you the most of them and just walk along it, avoiding any enemies (it was a massive mistake to halve your gems when you get hit, it should have been losing about 10 of them or something.)