The best bit of advice is usually - don't go chasing and catering to every fetish crowd you can identify and hope for success. Focus on a select few the you personally know and love. Catering to other people's fetishes never ends well. And your typical "harem, romance, rape, ntr, incest, futa, furry, vore, MMORPGFPSWTFBBQ" games don't really have a good track record.
Good luck on your game!
Good luck on your game!