You can join a clan once you have reached level 3. Being part of a clan gives you access to donate & request cards. If you donate you are rewarded with experience & gold.
You can also chat with clan members & have friendly battles.
If you are looking for a clan to join, search for ugvm
I'm level 6 at the moment & hovering around 925 trophies. Seem to be getting quite a few drawers lately.