Be sure to subscribe to all of these before connecting to the Garry's Mod server. This collection will also be updated whenever new addons are added, so be sure to check back here.

http://gtm.steamproxy.vip/sharedfiles/filedetails/?id=375760266

Also, if you want the Doom addon to work properly, be sure to download this and put it in your garrysmod folder: https://dl.dropboxusercontent.com/u/27048651/iwads.zip