Dianna, we've had good success with the rubberized borders. You first need to cut a straight line with a flat nose shovel or edger blade. Get down about an inch or two below the garden surface, lay in your edging and pins, then pull the soil back over the lip of the edging to keep it in place.
You can use bricks, rocks, or even flower pot. Here are several ideas https://www.hometalk.com/search/posts?filter=garden%20edging
I've used brick, blocks, and the rubber stuff. My dad did some with landscape timbers that have held up very well, over 15 years. Also, you can use plants like mondo, monkey grass, buttercups.
I've seen plates from the thrift store stood up on end, wine bottles, bricks, pieces of cedar slats, large rocks, pavers, metal, plastic, there are so many choices.