Dont have the money for CSS? Solution right here baby, yeah I stole it from moat but why would you care? 
I don’t know formatting here yet but if you want to reupload or pin this, feel free ^^
Map Errors
If you’re having map errors, the culprit is almost always Counter-Strike: Source. CSS is a game made by Valve that many map makers will use textures from in their maps. While it makes things easier for them, it means that the players will need CSS in order to properly see the map, but don’t worry, you can still get the textures without owning the game.
If you OWN CSS.
Make sure the game is downloaded and installed to your computer. Then, open Garry’s Mod and click the game controller in the bottom right corner of the screen. Then, check the box next to Counter-Strike Source. Note that you may need to launch the game again afterwards.
If you DO NOT OWN CSS.
This is going to be complicated for people who aren’t great with computers. Although you may be able to find the files online for free, that is technically illegal, so I won’t go into that method here. Anywho, you’re going to need SteamCMD. Get that from here: https://steamcdn-a.akamaihd.net/client/installer/steamcmd.zip.
After that is downloaded, create a folder for the program somewhere, and extract the zip into that folder.
Double Click “steamcmd.exe” in that folder, and wait for the downloads to finish. Once you see “Steam>” you know you’re ready.
Type into the window “login anonymous”. Wait for it to say “Waiting for user info…OK”.
Type into the window “force_install_dir css/”. It shouldn’t say anything after this command.
Type into the window “app_update 232330”. This is the actual download process, it will probably take awhile.
Once it finishes downloading, type “app_update 232330 validate”. This step is optional, but recommended, as can check for corrupted files. After this, you can type “exit” into SteamCMD to close it.
Now, look in the folder you made for SteamCMD. You should see a new folder called “css” inside of it. Keep this window open, as we will come back to it.
Go to your steam library. Find Garry’s Mod, right click it, click properties, then switch to the “LOCAL FILES” tab. Click the button that says “BROWSE LOCAL FILES…”. This should open your GMod directory. In this folder, go into “bin”. Scroll to the bottom of the page so that the file “vpk.exe” is in view. Keep this window open for the next step.
Back over in the SteamCMD’s CSS folder, look under CSS/cstrike for the file “cstrike_pak_dir.vpk”. We need this file. Drag this folder onto the file you found in the last step, “vpk.exe”. It will pop up a window, just wait for a bit, it is working.
Once the window disappears, you should see a new folder in the “cstrike” folder called “cstrike_pak_dir”. Rename this folder to “CSS Textures”.
Go back to your Garry’s Mod directory. You’re almost done! This time, open “garrysmod” then “addons”. Drag your newly created “CSS Textures” folder into here.
You’re finally done! All that’s left is to check to make sure it worked by opening Garry’s Mod. I know this was complicated, and I’m sorry for that!
Hope this helps
-fire
