What do you guys play mainly?
Make sure you all have High K/D over 1.50 plus.
Make sure you guys can win each match.
Make sure none of you camp (that wont make you legit, it will just make others think another camping clan).
Make sure your kills are higher then your deaths always (Try not to hit double digits).
Challenge other clans you know have 6 players or evenly as you guys and prove your skills.
That's all I can think of.