Make it an enjoyable experience. Happiness is priceless. Extracurricular activities count. Whether a club or athletics, it shows you are a well rounded person. And it may be your best opportunity to exhibit leadership skills.
Experience is experience.
You gain new experiences every day. You do not need to be paid for it to make it valid experience. Grades do matter. If you are reading this early, keep your grades high. If late, you will have to provide a very good reason if they are not at least a 3.0 or above.