I won't buy an adopt unless I think up a use for them. If I have an idea for what i would use them for then I'll definitely buy them, so long as I can afford it.

Usually its up to if the adopt appeals to my personal tastes also helps if its made from scratch, not just pallet swaps on a base

I usually only go for egg adoptables, just because I typically want to choose the species and some characteristics. I'm lame at coming up with patterns and more iconic physical details though, so egg adoptables help bridge that gap for me.

Nice, thick feet.

Also, ability to be popular on f-list, I imagine that is a more typical deciding factor.

Even more typically, a simple but appealing style that will translate well to other artists - ideally, to me, something that's not totally on any one edge/corner of the "standard anthro/chibi/critter" triangle.

For example, the snake and the robin you posted a while ago both fit all of those (except the feet ehehe.) Only reason I didn't go for the snake was the lips, which are not to my own personal tastes on funny animals. The robin just got dang expensive.

What, in your opinion, helps something become popular on F-list?

I suspect a good share of my adopts have ended up there since being bought, so I'm definitely curious.

Haha, uhhh that's a good question. People would say "being a female character," but honestly there is just almost a total lack of interesting males on there, and cute guys do fine too. (Especially, like, fairly-manly guys that don't just look like something they got from "male solo order:random" on e621. It's all baras and twinks, I swear.) I'd say the most popular characters are popular for one of a few reasons. Their design could appeal to a specific fetish - and, better yet, a power position, dominant or submissive - somehow. People tend to like that. Orrrr they could just be attractive with a big fat ass and be played as slutty. That tends to go over alright as well. (I guess in terms of an adopt "slutty" would just mean drawing them stickers with fuck-me eyes haha - snake's a good example of getting that right, probably.)

Also, stuff that they can design on a profile as inlines is probably helpful. That just means that they can easily cut it out so it's got a transparent background and stick it on their profile page. It's all the rage, these days.

Being setting-agnostic kinda helps, as well, although it's hard to balance that with giving them outfits.

The ability to do the dishes.

A combo of actually having ideas for them when I see them, unique character qualities that make them stand out against other chars, and some personality that's present in the adopt image.
I'll use em to rp sometimes but they're mostly geared toward my commission interests and if I'd be able to match them up with the existing chars that I have.

Another point is starting base price. I've seen some adoptables start at $80-100 which imo is too high to start out with.
I get that the artist has spent time on it and needs a ROI but if it' s an auction that's one helluva SB.
And I'm talking a simple, 1 image adopt, not like a full ref like you've posted.

I think its going to vary alot person to person since it matters on what they are looking for in an adoptable. I seem to notice that characters seem to sell really well when treated more as a blank canvas when it comes to their personality, profession, ect. It leaves the door open for the new owner to imprint upon the character and more room to grow after adopting the adpotable. Granted the other side of the coin is that people sometimes fall for a character due to the personality and details already imposed on the character. So it sometimes becomes a crapshoot on who and what people are looking for and want. I think you are doing a fairly good job with how you've been doing your adoptables because they seem much more alive than the usual "Claim in the comments what recolor you want!" that usually ends with several unsold characters. All in all, I personally think the best quality in an adoptable is making sure the character has some personality to serve as a foundation for the new owner to be able to build from. Id also say that making sure the characters are cute but you already draw everything looking adorable!

Personally I commission artists to support them but if I were to buy adoptable, I'd look for something original, as well as a good ref sheet.

Another one on the looking to fill character idea space... Though I don't think that helps very much.

Personally tend to go for interesting takes on naturallistic fur patterns over galaxy rainbow pixie kitty... Though don't mind a neon hairdo!

In all honesty, I have no idea why people get adopts so much. There is the way that DbD does it that I understand and is plenty useful where you give her some information and she creates a character from it.

That said, I have bought one adopt before, a maned wolf vampire like character. Dunno why, but I just felt like I must have him, due to similarities between my other characters, as well as differences between him and them.

I'd have to say though, the Adopts Im more likely to get is something useful. Like making a character for pathfinder adoptable.

To me it's important that it's a species I really like. If it's a species I'm not really into I probably wouldn't be interested at all? Like, a spider (I hate them) x.x; But big cats, birds, canines, otters, hooved animals, mustelids are all good! <3 Also important that the character has some unique personality or look about them (like clothing or accessories). But if they cost too much for my taste it's just a "Nope" no matter what for me. I'm an artist though so I figure I can make my own character if I like an adopt that much. Many people aren't artists so they would probably be willing to buy it regardless of price because they may not have any alternative option.

I like the idea of randomness with eggs but otherwise characters that aren't just literally palette swaps like some artists will put out.