You need to know the SRM of the recipe you will be brewing. If you have the recipe and it doesn't come with an SRM, you can enter it into a brewing software like beersmith or promash. If you are building the recipe yourself, use the software. They let you down load trial versions. Saisons and blondes are pretty low SRM, so they will use a low RA. If you are starting with distilled water, Add minerals until it gives you an SRM range that your target SRM will be in. Also, read chapter 15 (i think) in how to brew again. If you are starting with distilled water you may want to add some Ca for the yeasts.
I relistened to the Brewing Water Podcasts and got down the SRM to RA talk. And like you are saying, it sounds like I need a minimum of 50ppm Calcium -- what about the Sulfate to Chloride Ratios? Balanced for these styles?