Using cinder blocks for your garden beds is great because you can easily pick your height. If you want your bed close to the ground, just do in one layer and go for two or three if you want it higher and easy to reach. To make the bed stronger, push a length of rebar down through the holes on each corner using a sledgehammer. One in each corner should be enough when using cinder blocks for your garden beds, but you can always add more if you are worried.
You can also repurpose your cinder blocks as amazing cinder block benches that is also money-saving project. Use wooden boards and cinder block to build a nice seating area around your house; around the fire pit in backyard, patio. You can also paint the cinder block to make it more colorful or add throw pillow for more color and texture. See those picture below for another example.