question about a betta

Hi,
my little sister (she is 10 years old) got a male betta. she has him in a 1 gallon bowl. she changes the water every week. the pet store lady told her to use nutrifin bowl conditioner for bettas and nutrifin bowl cleaner everytime she changed the water. I am wondering if that is the only things she would need to do to keep the water good for him..or do we have to test the ph and buy conditioner for that too? anything else we need to add to the water?
this is the first time owning a betta and it would be so helpful if someone explained what we need to do to keep him healthy. (like when using tap water, how long we have to let it sit and what do we add to it before putting him in there)

thank you

eman