Step 1: Don't buy any special ingredients!
Start collecting the odds and ends of vegetables the next time you are preparing a meal. When you make salad, pasta sauce or any dish at all keep scraps such as the stems or ends of fresh herbs, carrots, zucchini, squash, celery, mushrooms, peppers, tomatoes, ANYTHING.
As you collect the veggie scraps save them in the freezer in zipped freezer bags until you have 2-4 bags totally full. Now you are ready to make the stock!
I generally don't cook meat so this is a vegetarian recipe but you could certainly include poultry, sausage, pork, beef, whatever kitchen scraps you think would make a tasty boulion. Bones from ham or roasts are commonly used to make stocks and bullion.