When you need to duplicate multiple measurements on a larger project, it can be helpful to use a length of 1x2 or similar stock as a story pole. Cut or select a piece that is longer than the longest cut required. Carefully mark the height, width, depth and length of various parts onto the 1x2. The story pole will speed up marking for cuts, and matching parts will be cut the same.
When buying quantities of standard fasteners, such as screws or bolts, buy a full box anytime you will need close to a half box or more. The second half of the box will be virtually free. For example, 45 individual screws will usually cost about the same as a box of 100 screws.