Rite Aid has seed packets for $.20 each. I was looking at the vegetables but I think they have flowers too.

Dollar Tree has plastic nursery pots - 10 of 3", 5 of 5", and 3 of 7", each for a dollar.

Home Depot has 18 gallon plastic containers for $3.89. These are made out of black #5 plastic. That is supposed to be the safest. Good for homemade earth boxes.

I've got a supply of the 5 gal pickle buckets from work, but I'm not sure if I need more space for indeterminate tomatoes.