Everyone wants clean showers - but paying for the formula is expensive. I've found a cheap way to deal with this situation. Maybe not cheap to start with, but well worth it in the long run.
Purchase the Automatic Shower Cleaner product (about $20). This comes with two containers of shower cleaner. Using this batch is a good start. Clean up the shower by hand initially to get the junk off, and then use the cleaner after each shower (one button push). You will notice that it does clean up pretty good, however, replacements are expensive.
Now here is where it gets nice and easy. After you have used both bottles - simply open one of them (they are hard to open because they have some reverse tabs on the inside of the lid - but they do come off) and pour in about 2 or 3 tablespoons of Jet Dry dishwasher fluid. Fill the rest of the bottle with water. And voila, you have a wonderful shower cleaner. Just tap the button after every shower and it will always look good!