Google it, i bet you will find a mix but it usually costs more to make it then just to buy it... In honestly, i just get a box from the dollar store (dollar tree) and it works just fine.
I used to make it and I thought it worked pretty good and was a great moneysaver. I could get all the supplies for around $20(enough to make at least 2 batches) And a single batch would last for 6 months. You only had to use a couple tablespoons at a time. The recipe I used had Borax, washing soda and grated Fels Naptha bar. And it did a good job of cleaning the dishes. But, my glassware came out so cloudy and milky, it looked etched.
After doing some googling, I found that my extremely hard water was to blame. And adding a couple packets of unsweetened Koolaid lemonade to the mix worked wonders! The citric acid in the koolaid is what did it. I also use lemonade koolaid as a cheap alternative to Dishwasher Magic(dishwasher cleaner).
I haven't made the homemade stuff since I got into couponing. I was able to get a bunch of dishwasher detergent(Electrasol) real cheap(almost free). But once that stash runs out, I'm going back to homemade.