Re: So I made a tumblr... Help?
Oh Boy..
First off, I'd like to point out how hilarious it is to me that you were a little bit nervous with putting porn on Tumblr. Tumblr is pretty much the go to social media site if you're looking for porn ;D As Yoshiki said, jsut make sure to mark things as NSFW.
Whenever you post something, list as many relevant tags as you can think of. People don't just follow people, they can also follow a certain tag. My tumblr, for instance, follows #CowboyBebop. So every time Someone posts something with that tag it shows up in my feed. If i find someone who's posting content I enjoy when it shows up, I will follow them.
As far as etiquette goes, I assume you are talking about reposting what other people create and things of that nature. If you reblog someone's post, it is absolutely okay. When you reblog it, people will see who you reblogged it from, so you aren't taking credit for someone else's work. I can guarantee people will do the same with things that you post. So, if you post something related to your game, maybe the latest DL link, make sure to also include a link to your Patreon or your Tumblr page so that people can easily navigate to the source of content. Outside of that.. Just don't be a fucklestick and you'll be fine.
Gathering followers is.. a little different. I would think that you don't want to gather any old followers, instead you want to gather followers who would be interested in your game. If this is the case, I would post things and reblog things relating to your game. Its been a couple years since the last time i tried FSA, but from what I remember, I would post things that you can tag with #fantasy or #pregnancy or #corruption and things of that nature. (All with the nsfw tag of course)
Some really popular content creators got popular by doing this. Someone who posts a lot of hentai will, a few times a week, say "hey, want to buy some erotic cosploy photosets?" Theres plenty of artists that will do much the same and then offer their talents on commission. Don't hesitate to post updates and releases with your game, but posting other things in between will help to gain more followers who might be interested in it.