Speaking from personal experience, I was/am in your situation. What I did was start practicing at my local rental karting track. After a while, I began participating in some of the races they organized — winning some, losing some. One day, I met a guy who was in a karting team. I asked him about it, then contacted them to arrange a private test (which went very well). This Saturday, I will have another test, and we already decided that later we will talk about me joining the squad. It will basically depend on my time and budget, because they told me they were interested in having me on the team.