It seems fairly simple to make your own characters and stages for MUGEN. They don't have to be fancy, but there isn't too much hard work involved making your own characters. I've seen cheap characters and "MS Paint" characters a lot watching the SaltyBet Twitch streams of MUGEN. Following the model of Kung Fu Man (KFM), I realize it isn't too much hard work to design a character for MUGEN. By the way, I was impressed at some 3D characters made into 2D and done cleanly with clean textures and animations. Like I saw a 3D Chun Li character that was done quite nicely. Unfortunately, I think she lost in a 3-0 sweep (most SaltyBet MUGEN fights are Best-of-5).
To that end, I am working on making at least one character and at least one stage. I want it all to be original- I'm not going to copy over any existing characters unless I am trying to use certain sprites and textures as test mules. I am even using Inkscape to build vector images to later trim down to be useful in MUGEN. As I'm learning to make material for MUGEN, I'm also learning vector art. So this is a learning experience for yours truly. If I do make something interesting, I'll share it here, in my blog(s), or even on my creative works site.
Besides these things, I am going to try to watch more videos of certain popular fighting games I am purely unfamiliar with. So when I look at stuff like SaltyBet, I can at least know what I'm talking about with some more popular fighting games and fighting game series.