When you first start home educating you are tempted to buy it all. Especially in math. I looked through what I had, and figured out what I used the most.
We use the Ones, Tens, and Hundred foam pieces all the time! I bought this when I was teaching, but found a similar one at Amazon.
These are items I think you should have to teach math: protractor, ruler, dice, calculator, tape measure, and a big die.
I love these fraction tiles. You can buy them as magnets, plastic pieces, or in a tray. This is a great resource and we pull it out daily while working on fractions. (I have pieces missing... get one with all the pieces.) I found another set with decimals as well.
For learning math facts we have used the Flashmaster for years. In a world of high tech iPads, laptops, and tablets, I like that the only thing you can do on the Flashmaster is math facts. No one "accidentally" does anything else. (I'm sure this doesn't happen at your house, but just in case.) It is a bit pricey, but I have many children and it has been helpful. We start each math lesson with it when a student is learning their facts.
The other math fact learning program I have used through the years is The Quarter Mile. It is a good program that simply reviews the facts. If you click on this link from the Homeschool Buyers Co-op, there is a video and more information.
Another great resource is linking cubes. Love these for counting, addition, patterns, and subtraction.
I have used my time manipulatives such as a clock with movable hands, my clock stamp, and an elapsed time board.
These are my elementary go-to math manipulatives. Which ones have you used the most?