Crear una tienda virtual

I want to develop a webpage related to sport races and fundraising. The project will be based on various sport races (ej. a campaing to fundraise money against cancer) and racers who will subscribed to one of the races trough this website and who will run to achieve funds for this concrete campaing. On subscription and even later,the racers will be able to send requests to their friends asking for support, and the friends will be able to enter this racer's profile on the campaing and pay with credit cards or paypal to support him running this campaing. There should be a scoreboard for money achieved for the race (top ten racers) and the same for each racer's profile. I already have the graphic design and most of the look and feel for the web. I also have a pretty good idea on the navigation map I need the web to be secure (like payment should be secure) and measures taken during programming to avoid hackers.