Yes most are invite only.
If a clan is openly recruting then its gonna be a crap clan.
The fact that you need to post here suggests you have no experience, therefore are new, therefore are not good enough to join any clan. Play the game for 30 mins and if you've any sense you'll be a master. There will soon be no competetive clans as they'll soon find out they cannot play the game competetively, due to reasons prestated. So go join a group of rpg'ers or something.