just start playing 6s if you wanna play 6s. just do it. join a team and also start playing newbie mixes/pugs. if you wanna work on your dm and mechanics then play mge, dm servers, or jump maps. the more time you wait the more time you delay in actually find out if you enjoy it at all. your ability will come in time whats important is that you start learning sooner rather than later. true for tf2 and for life
good luck and have fun.