I hope I don't come out as too harsh on this but here it goes, take it with a grain of salt and remember this is just my personal opinion, so you are free to take it all, take some or disregard everything as you please.
I think Dash sales did better than your other games was because Lustfire's art.
I think you need to improve the overall look of your games if you want to be successful. Your drawings lack anatomy and weight, they seem rather flat, and proportions are different between drawings very often.
If you have trouble with anatomy you should be copying photos, one way you can do this and still get stylized drawings is to get a photo with a pose you like, make a quick drawing over it using boxes, then make your own drawing using what you just learned from drawing over the photo.
I'm not a fan of turn based combat anymore, so I can't comment on that, but I can say that your competition in that field seems pretty rough.
In my humble opinion, you should chose to focus on a single game engine, either pick gm or rm and get really good with one, instead of being so so on both. Since I feel the rpgmaker market is a bit crowded, and some of the competition is brutal, I would recommend focusing on gm and it's wider possibilities.
Also, I think you should exploit Lustfire's art to the max, I think you should try your hand with skeletal animation, have Lustfire make you the base character and you split it into pieces and animate it, your Dash game would probably have sold a lot better if the game itself looked as good as the cg's. I could give you a hand on this if you wish, I have a few animated characters of mine I could give you for you to study, and aid you in getting to grips with skeletal animation. And you don't have to break the bank to get good looking backgrounds, some solid drawings + some flat colors or cel shading can do wonders in making a game look professional.
In the end, I have no clue how to make a successful hentai game, in fact I'm still just posting "generally positive feedback" so I have enough posts to make my own topic and request feedback for myself, so feel free to just ignore me, but know that I would like to see you continue making games and come to realize your own potential.