I just use MLP Arena and the TP, basically. The Arena suits my other collections well enough since we have the Dollhouse. I tried a few other doll forums over the years and none of them ever worked out. I was on the Monster High Arena for a while but MH isn't my focus anymore and I didn't like the buy-buy-buy attitude of a lot of threads. I also have an Instagram where I post all my toys. I mostly follow American Girl focused accounts since the only AG forums that exist either don't have any focus on what I like (photography) or are silently locking out new members :/
I'm in a handful of doll Facebook groups but I haven't posted in any of them yet. I avoid the big name doll groups (MH, AG, EAH, etc) and mostly stick to the vintage/antique focused ones. Less drama that way!