If you’re interested in tribal RP that includes interacting with other guilds and participating in RP-PVP alongside cool dm’ed plots, spooky loa rituals and other aspects of the awesome troll RP, I can recommend Hand of Zul!
We accept almost all troll tribes, however currently the majority is Gurubashi, Zandalari and Sandfury, with some Darkspears too. The idea behind our guild is to restore the legendary Empire of Zul to its former glory - all tribes united under one banner, without discrimination and without oppression from either Horde or Alliance(in other words, we can be considered as ‘neutral’).
Alternatively, I can also recommend The Darkspear Warband - as the name says, it is a guild that accepts only Darkspear trolls, and they are loyal to the Horde, of course. There is also The Jungali Pact, a Darkspear Druid order.
For troll RP in general, there are also Painted Shields and the First Empire who are more focused on the imperial troll RP rather than tribals. That is, they’re both loyal to the Zandalari Empire first and foremost, if I’m not mistaken.