I have to admit. I have never used a formal spelling curriculum in our homeschool. The first couple of years I tried...yes I tried to follow the curriculum. I'm not even going to say the two I chose as it wasn't the fault of the curriculum that we were unable to use them. Instead I found other ways to teach it using whatever curriculum we used for other subjects.
Math for example. When they were young and learning their numbers they also learned how to spell the numbers. When my daughter learned to tell time she also learned how to write the time. When she learned shapes she learned how to write the name of the shapes.
My son has learning challenges so most subjects do not come easy for him. I have tried teaching him to read using sight words and phonetically, and although it is a slow process, using both works for him. He knows how to read a majority of Dolch-sight words and now I am working on him learning how to spell them. While he is reading if he comes upon a word that cannot be sounded out (for example know) I write it on a 4x5 card and throughout the day I work on him reading it and spelling it for me.
With my daughter she has been a naturally good speller and when she does writing is when we work on trouble words. There are also a lot of free activities online to help with spelling. Last year I really liked trying out Big IQ Kids spelling program and this year we are using a different site that even includes online spelling tests. What's great about spellingcity is that you can make your own lists or use the ones that are already made. The learning is done through playing fun games.
Learning how to spell really doesn't require a lot of money or a formal spelling curriculum. It can be learned little by little while doing other kinds of subjects. How do your children learn how to spell?