I’m going to give a very cliché answer but one I honestly believe in –
Roll whatever sparks your interest/enthusiasm the most. Spending just that little bit more time questing, reading up or asking for help for a concept is more than worth it if it’s something you’re interested in or passionate about. Sometimes it helps thinking about a certain Loa or class you find intriguing and building a character around that, and then choose the tribe most fitting.
One really really doesn’t have to know all the ins- and outs of a race or be a lore-expert before trying their hand at roleplay, and you will find many people who will gladly help you out along the way. Feel free to give us a poke whenever you’d like some brainstorming on a concept, or join the Wardrums Discord ([Troll RP] Wardrums - Troll Community Discord 💬 ) where you will find many more troll enthusiasts more than willing to help you flesh out a character!
The only tribes I (personally!) do not recommend as a main character, especially when you’re new to troll roleplay, are Blood Trolls, half-breeds or more or less extinct trolls such as Dark Trolls. Blood Trolls are antagonistic, even for most non-horde trolls the server, so you will find little opportunity to be anything else than a villain and there’s (as far as I know, correct me if I’m wrong!) currently no community / a lot of RP opportunities for them, so you will limit yourself a lot. Dark trolls are, since BfA, mentioned to be extremely rare if not extinct, and it doesn’t hurt to be a little careful when throwing such concepts into roleplay, if only to keep the immersion of other players in mind.
Hope that helps!