12 inch paper trimmer - A good trimmer can be used to do a variety of tasks, from cutting photo mats to creating embellishments. Look for one with a retractable arm that allows you to measure 12x12 paper.
Adhesive - There are many different styles of adhesive available, but to get started you want an acid-free adhesive that will work well on both cardstock and photos. Common types of adhesive used in scrapbooking are tab dispensers and tape/adhesive runners.
Cardstock and Printed Papers - Select paper to go with the colors you wish to accent in your photos. Paper can be purchased either in packs or individually.
As you find your own scrapbooking style you may also want to invest in items such as journaling pens, stickers, rub-ons and other embellishments.