If you don't want to invest capital but still want to obtain some BTC, you will either need to earn it or be given it. Bitcoin faucets give a small reward for visiting the site, usually because of ad revenue the site obtains by the visits. The most reliable way to earn larger amounts of BTC would be to sell products or services in exchange for bitcoin (obviously selling products is similar to investing capital, but services such as freelance programming, etc. can pay well)