Before planting in a large pot you will need a pool noodle and one of these serrated steak knives - it makes it much easier.
Use the knife to cut the pool noodle into 1-2 inch chunks depending on the size of your pot. For some very large pots I used 2 noodles for each one.
Just put the chunks into the bottom of your pot. It creates excellent drainage, is lightweight and easy to deal with if you dump everything out to change things. It's also inexpensive since pool noodles are about $1 each. If you are really strapped for cash and your pots are large you can use empty plastic water or soda bottles. I did that 2 years ago to some large pots and it works fine.
I had gotten this little terra cotta bunny at a yard sale for 50¢ but I really didn't like the terra cotta color. So I splurged and bought this:
It was not cheap but I have plenty left for another project one day and my faux stone bunny was much cheaper than a real stone bunny would have been. Now I need to decide where to tuck him in between plants.
And this plastic pot got an update. It is years old and the plastic is getting brittle. So using my accent blue paint and green trim paint (just semigloss exterior paint from Walmart) I gave it a bit of pizzazz. The garlic chives a friend gave me look pretty happy now. Oh, and pool noodle pieces were used in the bottom of this pot too.