For my shelves, I used
4 QTY- 8’ long pieces of 1/2” oak plywood 16” deep
2 QTY- 1x3” oak 1x3 96” long (exact length of my shelf)
1/2” oak plywood 1 1/2” wide as shelf supports (you can use 1x2s as well) 4 QTY at 15” for sides and 2 QTY at 96” for back support
4-6 shelf brackets for extra middle support
Stain, glue, brads, and screws.