I have been summoned! (Thanks for the shout-out, Mordash. :D)
The Hand is always recruiting roleplayers, both experienced and completely new! We would be happy to show you the ropes of RPing because it’s an awesome and creative hobby. We have a big pool of active users and regularly run both DM’d events and spontaneous social RP. Here is our recruitment thread if you want to learn more about who we are and what we do!
Other currently active Horde guilds are the Convocation of Elrendar and the Beastmaw Warband. (Also the Coven and the Vigil, but I’m not sure if they’re active at the moment.) If you want to give Alliance RP a try, I will very unsurprisingly recommend the Botany Band for chill plant-related activities. 
Thaaaaat said…
It would definitely be disingenuous to try and paint Sha’glade Cartel as a bustling walk-up RP central. As an expat myself I can firmly state that the dynamics between the servers are completely different. If I had to draw an adequate comparison, I’d say that AD is a metropolis while SGC is a sleepy little village in the hills. This can be a blessing or a curse, depending on your expectations. If what you want from RP is to be able to enter an inn at any given hour and find spontaneous RP, SGC is definitely not going to satisfy that need. RP here is generally very guild-centric. You also don’t find the kind of variety that AD offers.
For me, personally, SGC is a dream come true. It’s very relaxed, it’s not crowded (important for a person who finds it difficult to focus, like yours truly), and the smaller player pool naturally results in a much more tight-knit community. I also feel it’s a much better learning environment for a beginner roleplayer, purely because with less people around a new player is generally able to receive much more attention. It’s also much easier to keep up with RP, which can definitely be hard in the beginning.
While SGC might seem ‘dead’ to an ADer, it’s actually far from dead–my guild for example tends to have planned events several times a week (we’re currently in new-patch phase, so normal event schedule will return once the DMs had the chance to play through the 8.2 zones and plan some storylines 
), but if you wish you can easily find yourself roleplaying every single day, as long as you announce it in guild chat.
In the end it’s a matter of what works best for you. If you’re happy with a small close-knit community, SGC is definitely a sweet little corner of the Internet. It’s been my virtual forever home, and I’m grateful I found it.
Whatever you choose, I hope you find much joy in RP. 