Question about reducing heating costs?

We are on a tighter budget this winter and I would like to try to reduce some of my heating bill. I have gas forced air heat. I already put plastic on some of the windows and have noticed a difference. For some reason there is a heat vent as soon as you walk into the house in the hallway. Directly on the other side of the wall is the vent that goes in my son’s playroom. If I put a vent cover over the entryway vent will that help more of the heat go into my son’s playroom? Another question, we mostly stay on the first floor most of the day and we have to heat all the rooms that aren’t even being used. If I turn my thermostat down a lot during the day and just use a space heater will that be cheaper than turing the thermostat up? Also my hardwood floors are very cold since the basement is directly below. I have area rugs down but they don’t cover everywhere. What can I do to reduce some of the cold coming from the floors? Any other suggestions about reducing costs would be greatly appreciated.