Heya! Glad you’ve decided to dip into RP. It’s the real endgame of WoW, you know!
I suggest taking a look here: WrA Information & Directories - #26 by Reinore-wyrmrest-accord
There’s plenty of guilds that are welcome of newcomers. Keep your eyes open for “casual” or “light RP” in the descriptions for something a little more relaxed.
If you have ideas for themes you might be interested in you can post them here and I and others would be happy to suggest some.