We only have 1 set of blocks and have had no problems. They are necessary though.
As for the DVD’s not necessary but the kids and I really like them. I have learned great tips for teaching math and the way he explains things, it just makes sense. The kids and I watch the video together and then the kids do their math. It is pretty hands off for me. I watch the videos too to make sure that I am teaching how he teaches, if there are questions, not my short cuts I learned years ago and confusing the kids, LOL.
My oldest is starting Zeta this year and math is the one thing we have not changed for school because it is hands off for me and works for the kids.
I always buy the teacher book and DVD used very inexpensively. The nice thing is that the older teacher guides and DVDs still work with newer student books. I have some guides with the old “comb binding” from I think 2004 it is and others that are the nice hard back TG.