You're currently on:
Diagramming
Picture your potential garden with sketches
The joy of not having a beautiful, organized garden is getting to create one. And there's no easier, more financially viable, way of figuring out what your options are, than sketching them. Sit down with a pad and pen (or even better, crayons or colored markers), have a cup of tea, put on some music and let your mind wander. Don't worry if your artistic talents make pansies look like action stick figures.
Don't be shy filling up the space in your container garden - a single red geranium will be lonely for friends of all shapes, sizes and colors. (Have you ever met a prejudiced geranium?) See what colors contrast or combine to your liking. Play with size and shape, height and texture. Make many, many drawings to see what works and what doesn't. Consider planting a combination of annuals and perennials to keep your garden blooming for months to come. And think about how your garden will look throughout the day, in different light conditions.
As long as the plants within a single container have similar light and water requirements, you can go wild.