Never forget this if you're looking to create a full on fantroll. They all needs dancestors and ancestors
Ex. Karkat- Kankri, The sufferer
Ex.Nepeta-Meulin, The disciple

Don't forget the theme and base the ancestor on that. Try and connect your fantrolls feelings toward another troll from their ancestors or dancestors past.

It is okay to have different personalitys for your fantrolls ancestors and dancestors just like karkats, and feferis they're all totally different. They should all have different personalitys, since well...they're different trolls. They all should have the same horns, and blood color.

Example from my own fantrolls. Her name is Laili, and her dancestors name is Kaira, her ancestors is the betrayer. Laili is a total airhead and is super hyper and usually doesn't call people out on their blood and show off her high esteemed blood either, unlike her dancestor and ancestor who take everything seriously and show off their blood whenever they please. (Kaira pic shown at top)

Please, please, please! Be as creative as you like with your A's and D's! They're yours! And no one else's.