You won't need to buy garlic if you grow your own!
Just select a nice plump clove (remember that's just one segment - not the entire bulb!).
Plant straight into a pot, keep it on a sunny windowsill, and water often.
You'll know it's ready when the bottom leaves turn yellow.
It's amazing just how much you can grow from the leftover bits of vegetables that you normally throw away, so give it a go!