Make sure you go to JoAnn fabrics when there Quilting Notions are on sale. Or use their coupons.
Necessary are rotary cutter, mat and 24 x 6 1/2" ruler. All these go on sale for half off often or use the coupons. Sign up on the internet for their sales flyer. Get the flyer in the store and usually there is a 50% coupon inside the front cover. Get a decent sized cutting mat at least 24" long so the whole of the width of the fabric can be on it.
Don't collect specialty rulers until you actually want them for a project. A 12" square up ruler would be your next purchase.