Geraniums are inexpensive to buy and plant. In fact, they are often grown from shoots clipped off a main plant. So, once you have a plant growing, grow more just by cutting off branches and planting them in containers filled with potting soil. This method requires some time to set up, as the clippings must be inserted into a container. The potting soil will also add some expense.
Begonias are cheap flowers to buy and grow. They are also very popular, so chances are you'll find them at a gardening center or online at a flower seed distributor. These flowers grow indoors or outdoors, so they are easy to tend to and plant. Start with a pot and plant your seeds inside before moving them outdoors for the best results.
A very cheap seed to buy, you'll find deals like 2,000 for $3.50 online. You'll also find these flowers grow with relative ease. Just plant them outdoors in well-tended soil and water them as needed. You must determine how much water they need based on your own climate and experiments, but the initial expense is very low.
The black-eyed Susan flower actually produces its own seeds, so replanting is not needed in most cases. This cuts down on your ongoing expense if you want to plant a large area of flowers. Black-eyed Susan belongs to the group of flowers known as self-seeding, which simply means they produce their own seeds. The group includes morning glory and purple coneflower, as well as the popular sunflower.