I've only been selling adoptables for around 2 weeks but I think I can give some advice on them. Most of my designs sell in 2 minutes so I must be doing something right lol. I currently only sell on Deviantart and the toyhouse design marketplace. I'd recommend advertising your adopts on the design marketplace if you're starting out. It's a great way to get noticed since forums don't depend on your follower count.
I strongly agree with Vlxen's comment. Starting off with cheap and simple designs is the way to go. I'd also recommend starting off with set-price adoptables instead of auctions. I feel like auctions are for when your designs become more in demand. They're kind of a hassle to participate in and maintain (in my opinion) so people might not want to put in the effort to bid on your designs in the beginning.
I'd also try to appear as friendly and personable as possible. A lot of adoptable artists make it too obvious that they're only doing this for the money. It comes off as a bit too greedy and turns off a lot of potential buyers. Respond to comments with sincerity and talk about your design process a little bit. In your description, you could write a little bit about your inspirations or the struggle of making them. Basically, don't come off as a corporate businessman, be the friendly local artist who just wants to share cool designs.
P.S. if you make that article message or ping me about it 👀