Landscaping ideas & quetions

We have a decent size backyard with blockwalls all around. Now we want to build a planter alongside those walls. The planter will be about 5ft from the walls, 2ft high x 100ft long). Since we can't afford hiring a professional to do it for us, we'll be doing it ourselves. Problem is we have no clue how .

We're not sure what type/shape of planter to build either. (Stacking bricks, or wooden beams, or stucco/concrete walls planter, etc.. ) Does anyone have any type of planter at home that you can share the pictures with me so I can get some ideas?

Thanks in advance,
Theresa.