Personally, I'm into the incest+harem+creampie+pregnancy combo. As for incest types, I like brother+sister, father+daughter, and on some occasions, uncle+niece (I'm a guy in my 40s myself). I only go for mom+son and grandmother+grandson if it's part of the "package deal" with my other kinks.
Also, with every harem story idea, you should account for the fact that people don't want
every girl you offer as a love interest. You should give the player the possibily to reject (remain as friends) with every potential love interest.
Some comments on a previous list:
-no default girlfriends at the start of the game. nobody wants that, every girl should be a conquest.
Maybe, maybe not. If well enough written, it could still work. Like a girlfriend who wants to share you (the MC) with other girls, and gets off on that very idea (and would even be willing to get other girls on board with the idea of sharing and/or being part of a harem).
-no 'best friends' of mc. unless you're making ntr nobody wants that other guy around. but this is more up to your taste than the other points.
Gay best friend could also work, though (like in
My Dorm). But yes, you should be careful with any "best friend" of MC is presented. If they're already in a relationship, make sure that friend's partner couldn't be a potential love interest to the MC (unless that friend is an impotent cuck who's unable to be with that partner sexually). Again, be careful when writing such characters, since you can easily write yourself into a corner on that aspect. The "safe" solution is to make that friend asexual or a potential gay sidepiece (if you aim for your male MC to be bisexual).
For inspiration on how to handle friends that don't interfere with your harem, I'd suggest taking a look at
Sorcerer by Talothral (no incest, but it has a harem) - there, you meet up with a friend group (from MC's military days) somewhat regularly at a bar/club, although this is more of a side story element. The friend group consists of two guys (and their respective partners) and a woman (who later
can be added to your harem).
For inspiration on overblown harem stories with fun elements, check out
Grandma's House and
Motherless.
Most importantly, though, write a story that includes your own kinks. Find out what your story will be about (taking inspiration from other stories, without copying too closely), make a rough outline of how you want your story to progress (just so you have a general plan going forward), and make sure that every kink and love interest can be opted out by the player without impacting the overall story too much. Find games you like, and include parts of what you like about them.
What matters is that you make a story that's your own, don't rush it, and try not let outsiders influence you too much on how you continue your story along the way. Sure, take feedback along the way, but only include what makes sense to you. Also, ignore the trolls. And when it comes to progress, don't set a too strict release timeline for yourself until you've gotten a lot of experience. A few good examples to aim for are
Grandma's House (mentioned earlier) by Moonbox and
Tribulations of a Mage by Talothral (who has already had several
completed stories out). Both have pretty consistent release dates (twice a month) with decently portioned out chapters/contents. A bad example to avoid is
WVM by Braindrop. The story is decent, but the developer has proven to be inconsistent with target release dates and progress goals they've set for themselves, and the game thread is basically punishing them for that (even mocking the dev for their reasons for flaking out). It has ended up becoming a cautionary tale of what
not to do when it comes to overpromising on progress.
In general, I've seen many examples of VNs on here that fall apart and/or get abandoned because the author lost interest due to how the development went off track, either by including too much of the feedback or letting the feedback get to them. Make sure you don't fall into that trap.
BTW, if you plan on gaining monetary support during development, make sure incest can only be activated by adding a "fan-made" patch (examples: My Dorm and Grandma's House, mentioned above) or by manually entering relationships either at the beginning or when the character is introduced in the story (example: Motherless, mentioned above). Patreon and Itch have been cracking down on adult VNs lately, especially when incest is included. SubscribeStar also technically has this disallowed in their terms of service, and even though they've been more lax in enforcing this, I think they won't hold out too much longer.
