Whatever your passion is, that’s the direction to go. You have to genuinely love and be excited by the product to best sell it. Your friends will see your excitement and trust your judgement. People buy from people who they know, like & trust (remember that saying?). If you join a business ‘just because, it sounded good’ then the chances are you will fail before you have started, you have to WANT to promote the product and share that excitement with others.