There is no single best long gun option for a first time gun owner. The biggest factors for most first time owners is being comfortable using the firearm and how the firearm is going to be used. A bigger/heavier firearm tends to make the most pleasant shooting experience with respect to every caliber. The amount of training needed to operate different types of long guns varies as well. A larger/heavier bolt action rifle may be the simplest in terms of operation, provide a more pleasant shooting experience depending on caliber, but would typically be used for target shooting or hunting. A long gun for self defense may be some variant of shotgun or some type of semi-automatic rifle, but both can also be used for sporting/target shooting and hunting as well.