Each subreddit can decide its own rules for posting. Where are you trying to post to? Have you read their rules?
There are 2 types of karma on Reddit. Comment Karma and Post Karma. One is from making upvoted comments, the other from upvoted posts.
If you require 10,20, or even 100 Comment Karma for your account before you're allowed to Post to a specific subreddit then you should start making useful comments around Reddit.