This frugal hint is one that meets all those criteria and is very simple to implement.
In our family, we use store bought liquid hand soap always buying the jumbo size bottle to refill all the small hand dispensers in the house. Recently, I've found a way to make the jumbo size bottle last well over 10 times longer.
Just purchase several of the prefilled foamable hand soaps from your local store. After you use up the soap in them, simply reuse the foaming handsoap dispenser by adding 2 teaspoons of the liquid handsoap and then slowly fill the individual hand dispenser with water to about 1/2 inch below the top of the bottle. Invert the bottle several times to mix the water and soap ... and you're ready to go with a whole new bottle of foaming soap.
If you like your foaming soap a little thicker, just add an extra teaspoon of liquid soap to the water. I like the foam because it doesn't slide off little hands and right down the sink. It sticks making it easier for little ones to wash their hands successfully.
I love this idea because in it not only saves money, but also reduces waste. That's ten less plastic bottles that will be filling our landfills! Multiply that by the number of bottles of soap you will use a year ... and multiply that by years ... you can see the impact that this one little change can make.
Of course, you can use this idea with your favorite liquid hand soaps from Bath & Body and make them last much longer as well.