$40 too much
I don't understand why you would think $40 is too much to spend, every month on getting your dog groomed professionally. You have to remember they have tools that not everyone at home has, and if you're going to a good groomer they will do a much better job than you could do at home. They cut the dogs nails, clean the ears, empy anal glands (some do, some don't), bath with high quality shampoos and conditioners, use dryers and correct brushing methods to pull out dead hair along with the trimming or clippering. You will find the cost of equipment can add up quite quickly. My suggestion would be to do the dog yourself every other time while you're learning.
That being said, I would recommend that you check out the website for petedge (
www.petedge.com). For shampoos look for something that says it does not have detergents. For grooming at home, you could probably get away with using their brand of products for scissors, mat rakes, combs, brushes etc. They're a little cheaper and will do the job for you.
I think its great that you want to take part in keeping your dog's coat and skin healthy.