Basically, what Shogganosh said:
The Ashen have a strong blood elven/nightborne presence. Their GM is very chill and friendly. There is also the Grimtusk, the Blood Howl and the Bloodsong - military Horde guilds which welcome elves from all backgrounds.
Your best bet is the Horde discord. It is where RP Gatherings and Campaigns are advertised.
Lastly, for nightborne-only, there is the discord server I run. It is a place where people can go look for casual RP, create contacts with other nightborne, and you will usually find 1-2 events per month, even if I plan to keep it slow during summer.