I know that in order to understand recursion one must first understand recursion, but how can I build my reputation enough to post or vote or comment or anything when all these things require reputation to begin with?
You don't need reputation to post a question or an answer, which is the most common way to gain reputation.
Here you have information about specific privileges - https://stackoverflow.com/help/privileges
And here you can read about reputation system - https://stackoverflow.com/help/whats-reputation
You don't need to vote to gain reputation. You only need to post good questions and answers; and that requires no reputation at all.
While sometimes voting may be skewed towards the high rep members, usually it isn't and it's just as easy to get rep as a low rep member if you write high quality answers.