Geez you guys are making this way too complicated for a betta fish. They need nothing fancy.
I worked at a pet store for 5 years. People who started messing with their water always came into problems.
Set your filter up. Change the water on a weekly basis and change the filter probably every 6 months. Bettas are NOT dirty. They are easy fish to take care of. They are what I call a "gate-way fish" to other fish tank set ups.
When and if you upgrade to a bigger tank with other fish, THEN start messing with the water. PH levels should be fussed over if you own discus or angelfish. BETTAS ARE HARDY FISH. A lot of people buy them to help establish good bacteria in a brand new tank.
PLUS, you should have your water tested first to see if you even NEED to start messing with water chemicals.
People kill their fish all the time because they think something is wrong with their water. Let the tank cycle. It takes about 4 weeks for it to cycle. You really need to do water changes right now and adding your dechlorinator. Almost every single brand of dechlorinator already has a stress coat in it. The more crap you add to your tank the more likely your fish will get stressed out and die. If you want the best dechlorinator out there, then get PRIME by Seachem. Its expensive, but it has a lot of good properties in it INCLUDING an ammonia reducer and live bacteria.
Get your water tested FIRST before you start buying PH kits and messing with chemicals. You'll be happier with a less high-maintenance tank. Once you adjust your PH, you have to stick with it and CONSTANTLY check the levels. You might as well be doing salt water if your going to be THIS finicky.