If possible, you might want to buy certain items with cash. This makes it more difficult to track your spending habits, and helps prevent your identity from being linked to the item you purchase and the activities for which you use it. It also helps you to prevent others from finding out when and where you bought something.
If you must acquire and use a credit card for online purchases, consider the idea of using one particular credit card for online transactions. This does not eliminate your traces but may help isolate those purchases from your other other spending habits.
