If you're on a really tight budget, the cheapest option is hardy annual seeds - sown outside where you want them to grow, in patches. These will flower this year - have a look at the choice in the seed packet section, but make sure you pick hardy annuals, not half hardy. Also, remember to put a few seeds of anything you do plant separately in a pot, labelled - that way, you'll be able to tell the difference between the seeds you've planted and weed seedlings as they grow. The drawback with this kind of planting is you will have nothing to look at in the winter - for that you'll need a framework of shrubs, preferably small and large and mixed evergreen and deciduous.