I can't speak intelligently about Instagram except to say that it's not my own cup of tea. As for FetLife: I'd certainly recommend creating an account and familiarizing oneself with the place. 95% of FetLife is amateur porn, plain and simple. I joined a few local groups and started following a few local ABDLs, as I was interested in knowing about munches and events in the area. I ended up unfollowing almost everybody though, because whenever I logged in my feed would be a wall of dick pics and one-handed comments. And despite being male, straight, in a committed relationship, and putting all of that on my profile, I've been hit on by other guys, asked to come over and change people's diapers, etc.
So as I see it, it's a bit unfortunate that FetLife is the place to look for munches and other meetup opportunities in your area. But it is. I still log in regularly to check the groups, but that's about it.
I have a couple of close ABDL friends with whom I've exchanged messages almost daily for years. Both are people I met here on ADISC. There are many more ADISCers I think of as friends, and I've even met some of them IRL. I very much favor a long game when it comes to making friends, and I find a forum like this to be a great venue for that. Versus a stream of there-and-gone one-liners, the contributions you make here "stick," and you can therefore paint a much clearer picture of yourself over time, in addition to more clearly perceiving your forum-mates. You do have to invest yourself, though. There's nothing objectively wrong with coming here and posting one-line questions and answers, but as in so many other situations, you'll get out what you put in.