My favorite garden bed for planting in our garden is the Vita Gardens 4×4 Garden Bed With Grow Grid (link to Amazon). When we first started gardening we built our own garden beds out of 6×6 pressure treated wooden beams. We still use those in fact. But these garden beds are so much easier to assemble and plant in.
In fact, they require no tools to assemble and the grid allows you to easily keep plants separated. This is super handy when we have plants next to each other that require different amounts of water and nutrients. Also, if you buy multiple units, they can be attached together to make any size garden bed you need.