I'll be short and sweet with this. What is the best and/or lowest price you should sell pets at?

Look on the advanced search (while on this forum page, you can see the link to it on the left side under the search bar), and filter for what your pet is like.

For example, last I checked, ny'venes were generally 10k a piece at the lowest price regardless of whatever traits they had, so I priced mine 10k at the time.

What Flute said, using the advanced search gives you a good gauge. If you think your pet is worth more because it's themed/have nice coloration, you can price it higher, but it's probably better to post in the pet auction forum and advertise that you're selling those pets.

Just note though, there is a release competition going on, so if your pet is priced lower than the current lowest, chances is that someone will buy your pet to release. If you're ok with that, you can earn a bit of gold. Else, it'll be better to price your pet higher for now.