I dunno if this has already been posted, so i apologize. what water temperature would be good for my comet and gf? i can't remember having a heater in my old tank when i was younger.

Most people don't have a heater. Some people use them in the winter if they live somewhere where it is very cold in the winter. I, myself, have never had a heater and my goldfish are over 3 yrs old. Some people prefer to keep the water at a constant temperature, it is up to you.

i probably would wanna keep it constant because what happens when you do a water change, would the fish not get a little shock?

As long as u put the new water in gradually, it's fine, especially in bigger tanks.

As long as the temp of the water you are putting in the tank is the same temp as the water in the tank everything will be fine.

Summer or winter the water from my tap is always cooler than the goldfish tanks so I just top up the new water in the buckets with some hot water from the kettle.