You can build your own from wood obtained from Home Depot or Lowes. I would use 2 X 8s is you can dig a bit into the native soil. I prefer something prettier. Here is my raised bed.

I have the Greenland Gardener brand made from recycled composite materials and love them. I've had some of my beds for 12 years or more. They are like tinker toys for grownups and super easy to put together. I've gotten them direct from their website, from Amazon, and from Home Depot depending on sales/shipping etc to get the best price. The one downside is that if you try to relocate them you have to be really careful about taking them apart. I had one board crack where it slid into the corner piece. I've had others come apart with no problem.

Type of construction would depend on what you plan on growing as depth of raised bed, would help determine structure. Also, is it flat, or are you building on a hillside.

I've currently use cinderblocks and pressure treated bordered beds at my current home. And previously, used rough cut logs when I lived in Maryland.

Home Depot 12” deep Doug fir its. 10 ft long so get it cut into 4s and2s to get a bed of 2x4z. The easiest for a start bed.