Did you put fliters in the fuel line? Anytime you find rust, cleaning it once won't do it. It will stop you again.
Did you clean the vent in the fuel tank cap?
making a gasket is kinda hard for a carb. If you are going to try it you really need to go to the hardware store and get a few sheets of material. You really shouldn't expect any more pressure in the bowl than gravity sucking the fuel in.
Prolly not the spark plug.
Is your choke working?