I am going to use bottled water so I do not have to worry about the tap one beeing not too clear (Here I can find some at 0.20-0.30 $ a liter). Since bottled water has information on minerals in the water I want to take advantage of that. Which mineral should be there and which shouldn't be? What about pH or anything else?
The target mash PH is between 5.1 and 5.5 (again, not the water PH, the mash). From that comes that depending on what you are brewing you may need to make different mineral adjustments to reach the target PH. You may also want to try to emulate the water of a region that produces the style of beer you are brewing. John Palmer explained it all very nicely on his book