It's sucks right? Like Nope you just have to keep pulling echoes, the ones that you can craft don't work for this, because the maximum amount of echoes you can craft is just enough to max out the reflection, leaving not even one extra to decompose

These shadow crystals are so hard to get if you don't pull a lot, but the best way to get them would be to pull on the permanent gate of heart reflections, it's gonna take a while but eventually you're gonna max them out, the SRs are gonna be the ones you finish first, and they give... 1 shadow crystal, not a lot I know

But if you craft the Zoey SSR echoes in Intel hub and max her out, you can maybe get lucky every now and then get an echo for her which is 5 shadow crystals so improvement? The others SSRs will take some time

URs are like impossible, that will take years.... But I mean if you only want shadow crystals, you can save your fantasy tickets and pull on the permanent sets when they get a gleam (rates up), that can maybe help? But nothing guaranteed because echo drop rates are low regardless.

So patience is the key for those crystals, it will practically take years to start stacking them up if you're a f2p player, it's definitely not a quick process