Found out dollar tree has these stackable planters with 3 spots in each level and you can buy as many levels as you want. I'm considering getting 3-5 levels since they're only $1 each. I know they might not last years but it'd be for experimenting anyway. They are only 5 inches deep so I'm trying to figure out what I could potentially plant in there. Strawberries would probably work. Maybe some herbs. Would peas or beans work? Any other ideas?

I've actually used them to start mail order perennials and bulbs. The plants start doing their growing thing while I get their new home ready. They have the chance to develop a decent root system, but because their in pots, they're easy to transplant.

Last year, I used them for basil and mint to create a vertical herb garden. While I have a 1/2 acre lot, most of it is partial to full shade. Having the ability to go up really helps.

If you are thinking about going higher than 5, consider putting a piece of pip, metal or pvc, down through the centers to add some stability. The easiest way to do it is to stack the empty pots just like they are in the store, and drill a suitably sized hole through all of them at once. That way, they're guaranteed to line up when you actually stack them.