I think the current driftsmelt system is fine, but would gladly accept any reduction in 5km distance and number of stones you can hold (Best if each stone type can have 9 (more is even better) of each, instead of total 9 only). Proably a small request is to be able to marked skills that you want, so that it cannot be accidentally deleted.
Agreed with hyji6225, I have played in several gatcha games, and there is a cap like after 100 pulls, you are guarantee a 6-Star card, but I seldom get the luck of getting the ones I wanted (usually are the high tiered ones) but got the lower tier of the 6-Star. But sometimes I got the ones I want, then I started getting duplicates of it. I think gacha is all down to luck. I have smelt like 15 stones on a piece of armor, but still not getting the skill I wanted, but my son got it in around 6 stones. This is so demoralizing.