Don't fall into the trap of thinking that you have to create a bonsai from the ground up. Although you can definitely grow from seed, or cuttings, that is the longest route available to you. Instead look for established material from which you can work.
This could come from many sources, potted 'houseplants', nursery stock or collected material. Instead of getting a small plant and growing it up, get a big plant and cut it down. Make the smallest bonsai from the stock at hand and you will be years ahead of the game. Of course you can do both, which is what I do, but don't limit yourself to a single approach.
One of the best sources for inexpensive, or even free, material is old, unwanted landscape material. Look for stuff like Yews, Boxwood or even old Barberry.