Character, Tag, and Signature Art

So I'm relatively new to the game, but would love to have my own custom tag, signature, & character, however I have no idea what some of the things mean on the character buy/sell boards. Like I assume that SB means starting bid, but I've seen other initials and can't figure them out. Also, when people are offering to make tags for you, do you have to have your own character for reference? Or how does this work? Help??

MI = minimum increase
AB = auto-buy

Yes, typically you need your own character reference sheet that you either bought or created yourself to get tag recolors. Some people may accept photographs of real-life animals (that you own; you can't just use an image from online) but most do not because the images aren't always very clear.

Hope this helps!

SB = Starting bid
MI = Minimum Increase
AB = Auto Buy

Yeah, like Raptor said, you typically need a character for them to reference. Or sometimes the artist can come up something for you if they're willing. Just based on you giving them things you like about a horse's color. Blue roan paint, green eyes, blaze, etc. Sometimes people auction off characters they've made, or sell characters they no longer want that you can buy. You can also get characters by people doing mystery adopts.