Just click on the links to go to the collections and click "Subscribe to All" on
both. They will be downloaded when you launch the game for the first time, so launch the game before hand.

https://v1.steam.hlxgame.cc/sharedfiles/filedetails/?id=608641127

https://v1.steam.hlxgame.cc/sharedfiles/filedetails/?id=2567075141

Install CS:Source to ensure all the textures can be used. If you DO NOT have CS:Source you can get the texture packs from gmodcontent[dot]com and follow the steps below

Steps:
1. Download the content you wish to install. It'll download in a .zip file format.
2. If you haven't done so already, install WinRAR or WinZIP
3. Open the .zip file you downloaded from this website.
4. Navigate to your local Garry's Mod addons directory.
Open Steam, navigate to your library, find "Garry's Mod" and right click and select "Properties", Goto the "Local Files" tab, click "Browse Local Files". This will open the location of your game. Then, open the "garrysmod" folder and then open the "addons" folder.
5. Open the WinRAR or WinZIP window and drag and drop the content folder into your addons directory.
6. Restart/Open your Garry's Mod
7. That's it! You've now installed the additional content.