Thanks for the input, Krenko. I did some more thinking on the matter, and I think part of the problem is I'm trying to build a Magic set on a pre-existing world that I created for roleplaying and my novels. I've only ever completed one set, and that one just didn't feel connected really. The problem is Magic is all about resonance now, so each world they build (or at least most of them) has this strong flavorful thing that most people are familiar with that gives it its richness and focus. Innistrad was about gothic horror, which most people have at least passing familiarity with, and now Theros is Greek mythology. Same thing applies there.
I feel like if I build sets on worlds I create that don't follow a huge, well-known trope like those, it just feels like an older Magic expansion like Mercadian Masques or even Odyssey, where it was on a totally random world that was just kind of stereotypical fantasy. That's pretty much what my worlds feel like to me. That's alright, I suppose, but it just doesn't feel like a modern set. But I have this really cool story I want to tell and the world I made perfectly suits it. It just isn't a world that's going to feel very recognizable because people won't know anything about it.
But ultimately, I guess even that is a good enough starting point for a first real crack at a set. I shouldn't expect it to just be amazing I suppose. And being a one-man team, while it gives me some control that I may not otherwise have, also makes it a ton of damn work, since I like to follow a design skeleton and be all semi-pro about it. But oh well. I have the white commons and some of the red and green ones done, so I'll probably make a topic about the world and whatnot and start posting the cards fairly soon.
By the way, what is trash fantasy?