Any type of container will make a flowerpot. The bigger the better because the soil will not dry out as fast. The trend is to use old farm containers like buckets and wringer washing machines and plant flowers into them. The larger the container, the less you will have to water it.
The most important thing to keep in mind is drainage. Either drill in drainage holes or layer the bottom with small rocks or Styrofoam so the water can drain out of the mix. To prevent the holes from plugging up, use a cheesecloth or milking filter (if you can still get them) over the holes.
As for the potting mix, use a high-grade potting mix to allow for water draining so the soil is not soggy.
Now select your style. If a farmhouse style is to your liking, use old rusty buckets and other “antiques”. If your home has more a modern look, metal or ceramic colorful pots may have an appeal. A brick home can use terra cotta containers.
Before selecting your plants, decide if they will be in sunny or shady areas and select accordingly. Use them on the front porch, patio, deck, steps, or along walkways.