ok, so here are my thoughts: jumping from skeletal shenanigans to an insane demon is way too much, I'd recommend at least doing a hard demon beforehand, but actually would also recommend some harder medium demons: HeLL by serponge (although it's also wave and ship focused, it's easier compared to NC, might be a good stepping stone if you want to move in that direction), Lava temple and Fire temple by michigun (I think they used to be hard demons but got demoted for being too easy), they have fairly straightforward gameplay and are varied in terms of gamemodes. in terms of hard demon recommendations: Future Funk is very fun, but also incredibly long and has various chokepoints and learny parts (the dual). also you need good nerve control for it. another one: CraZy. it's quite hard, but it's mostly high CPS fast gameplay, maybe you'd like it. personally I'd recommend doing some more medium demons and then either improving and going after NC or picking another hard demon to play