Like, can you use the Unity Asset Store for assets?

"Make your own stuff, even if it's not as pretty, it'll be yours!"

If you buy stuff from Asset Store you will have the license to use it. So you can use it. But you should not use it without license.

You can use assets if the license allows so :) We always say make as much as you can yourself, it'll be better practise for you, but yeah assets are allowed!