Here’s an example if an adjustable shelf I made that’s very inexpensive. You can make this project whatever size you need. I used two 2×6 for the legs. I cut dados every 9” slightly wider than the plywood shelf. I used my router with a templete bit and a jig that I use when I make bookcases. Then I ripped the 2×6s in half to give me four legs. After that I routed the outside of the legs with a roundover bit.
For the shelving I used plywood cut to the size shelf I needed and then drilled two pocket holes in each corner on the bottem side. I then installed T-nuts and carriage bolts at the bottem of the legs so I could level the shelf. A couple rips to brace the back and you’re done fabricating. Assemble by installing the top and bottem plywood shelf, stand up, level and plumb the unit securing the X-brace. Then install plywood shelves into the desired grooves and fasten.
-- Darrell, making more sawdust than I know what to do with