Wait three days. Most subs only restrict age, and not by a lot. For karma, post some funny/interest replies to trending comments. (Or even a meta reddit joke will do it; Cbat is a recent one).

Only the biggest subs (or those with certain demographics, such as discussing social politics) need to control karma posting. And it's entirely to stop spam, sock puppets, and harassment, since making new accounts is so easy.

Subs dedicated to past times (tools, video games, hobbies, etc) tend to be very open since a lot of their traffic is people asking for help. eg: going to /r/marijuanaenthusiasts to identify an interesting tree, or r/OutoftheLoop because everybody on reddit has been talking about Cbat.