What is the best soil mix for a raised bed?

You can use the garden soil from miracle grow

You can mix your own with 4cu ft of peat moss, 4 cu ft of vermiculite and 5 different types of natural compost. It will have all the nutrients you need for the next 5 years with no chemicals. It will not pack down and it keeps the airflow to your plants.

Any commercial garden soil already has a mixture of components for good drainage and nutrients. A do it yourself mixture would have soil, sand or vermiculite and some peat moss.

There are two common types of soil that you can buy, planting soil and potting soil. You will want the potting soil. Here's a link for some info

https://www.facebook.com/scrolltrellis/ ; Look for the Soil Basics Video with Shirley Bovshow She is also on YouTube. Sorry I don't have the link handy.

I amend existing soil with compost, and vermiculite or perilite. I used to use peat moss until I learned how the boggs that it comes from are being depleted. Sand will lighten it up. You want it to be lighter so the roots will push through easily.

I also add cut up banana peels (potassium) , broken egg shells (calcium and magnesium) and coffee grounds. Mix it all up and viola! Depending on what veggies are planted, the soil does need to be amended. And veggies need to be rotated as certain veggie plants deplete the soil of certain nutrients.