I initially boiled everything once, then used the dishwasher after that. This is the same thing that I plan to do this time around as well. If you are using bottles for pumped breastmilk, check on the bottle box, they normally have specific instructions.
Honestly, I had a sterilizer and used it maybe 3 times, then decided it wasn't worth my time. I burned myself on the steam every time (probably user error, but still annoying), then they were super wet and had to air dry or towel dry for a long time, plus I didn't feel they were any cleaner than they came out of the dishwasher. I found my sterilizer to be a waste of money and quickly donated it to someone else.