Need mods

I’m fairly new to gmod. I know my way around the game but for the life of me I cant figure out spacebuilds. Or stuff with resources. what do I need for these things? I dont do much online games, its mostly just single player. What addons or mods or whatever do you recommend for gmod singleplayer? Or multiplayer gamemodes that are still playable/fun for single players?

(also if this post is in the wrong section, go ahead and delete this I’ll get the message. I dont quite know where to post it)