I use RO for everything. The Midwest US sits on a giant limestone cap, so our water sucks for brewing. I can get RO cheaply at a Kroger 3 minutes from my house. They also carbon-filter it, UV it, etc. It's a clean slate. It reads TDS at 0.
For a normal 5 gallon batch, add 1 tsp CaCl2 to your mash water. This will cover most of what you ever need to do. If you are making an English bitter or something else with a crisp finish, use 1 tsp CaSO4 instead. Use a blend of them if you want, but 1 tsp is about all you need for proper conversion.
Hit your sparge water with 1/4 to 1/2 tsp phosphoric acid per 5 gallons. Check the pH; you want it below 6 at sparge temps (but above 5). The pH will read about 0.4 higher at room temp than sparge temp.
Check your mash pH the first few times you brew to make sure you are in a good range (5.1-5.5 at mash temps). Wait about 10-15 minutes before you take your reading. Mash pH reads about 0.3 higher at room temp than at mash temp, so take that into account if you cool your reading.
If you make a starter, use yeast nutrient (I use Wyeast brand). Some extra in the boil will help fermentation as well. Follow the label dosage.