You get a guild bank once the guild leader has enough Astral Dimonds to buy it. I guess there are some other benefits as well, although I'm not sure what they are. Still getting used to the game myself, 26 hunter dps for me.
I'm level 60 SW, and I got 100k AD and have my own guild called 'Dovahkiin' lame name I know but we have 3 levels 60s including me and are into both PvP and Epic Dungeons. Feel free to message me on Xbox if you guys wants to use this as hour base guild considering I nearly have the AD for the bank