A MySQL database would be ideal for storing all of your information. But since you are relatively new to PHP and SQL I would go to http://www.hoptscripts.com and find one that fits your needs and configure it accoring to the instructions.
You're hosting company has to allow MySQL for you to be able to create or install MySQL databases. Or if you are running it off of your own computer then you would just need to install MySQL. The documentation and files to do so can be found at http://www.mysql.com
Hopes this sheds a little bit of light.
EDIT
You may also want to take into consideration the need for a SSL certificate for credit card transactions. You will also need an agency to proccess them for you like Verisign or CCBill.