[grannyknot]

As mentioned above, insulation is the best bang for your buck. Light bulbs are an inefficient to heat a space, you would be better off using that electricity to power an oil heater.
Natural gas and propane are still the cheapest sources of power, I use an 8ft propane fired infra red tube heater on the ceiling with a small fan mounted in front of it to circulate the heated air around the shop.
I also glued 1/4" plywood to the concrete floor and that really helps knock the cold down.
On the really cold days I pull out the BBQ propane tank and fire up the convection heater, 15 min of that and the place is toasty warm.
I have so many cracks and gaps in my old garage that fresh air exchange is never a problem.