By Kindergarten level do you mean the primer, and Alpha for first grade? My daughter is also 6 and knows how to add fairly well, we started in Alpha and she’s whizzing through it which your daughter probably will too, but will slow down about halfway when it gets harder. We’ve always skipped the Primer, because some of it is very advanced for a Kindergartner in my opinion, and there is so much repetition in Alpha so we just do Alpha.
Also, we use overhead sheets with dry erase markers in our workbooks, then reuse them for following children to save money.
Hope that helps, Adrienne