I usually aim for at least 50-75 ppm but it can be higher sometimes. I use about 5g of gypsum plus a little CaCl2 in my German. I have to use one or the other in a completely pale beer for mash pH because my water only has about 17 ppm Ca in it untreated. That goes for strong Belgian goldens, tripels, maibocks, helleseseseses, etc.
yeah - I'm starting at 6 ppm Ca. I can get the mash up to 75ish but I'd have to treat my sparge water as well if I wanted to get the wort up to those ppm levels.