You'll definitly want to use a database. It will scale better than your file system and should be much easier to use and faster.
Plus with databases, you'll be able to do advanced things with the raw data like create reports and searches, and statistics, and so much more.
I learned both PHP and MySQL in one evening, and over the next month or two created a 6,000 line eCommerce site.
Don't be intimidated by database systems like I was, after you use it you'll be glad you did. Just get a good book. I'd recommend MySQL by Paul DuBois if you want to use MySQL.
Good Luck