You will need to install the textures he said are "Required" before installing to make sure it works to the best of it's ability. It is also a good idea to install the game "Counter Strike: Source" since some of the items rely on the textures of that game.

Some textures may also be removed from the Steam Workshop or have not been updated by the original creators, you can get an "Error Hider" add-on if there are a lot of errors annoying you (but most of them will not hide missing textures).