I replaced an exhaust gasket today (piping connected to the muffler)

When i removed the old gasket, i found two gaskets, but i only replaced them both for one

Also i didnt have any exhaust gasket sealent, so i didn't use anything at all

My questions are:
-Do i need to use two gaskets or is one ok??
-Is it ok if i continue driving without any sealent on the gasket??

All help will be appreciated
Thanks
Steve