RenaeC said:...cinder blocks
When I was young my dad hammered into my head the difference between cinder blocks and concrete blocks.
Cinder blocks are usually less expensive and much lighter than concrete blocks. I like your idea of building the beds without tools and having beds that can be moved so you can relocate your garden if you move.
If you contact some of the companies that manufacture blocks and ask if you can purchase the "seconds"; the ones that are not perfect, a bit chipped or the wrong color, you might get them for less money.