If you want to make pk appealing to the public player, you need to do 2 things.
1st, make them relevant to the server somehow. Maybe rework the economy, so it is heavily dependant to civilian classes, thus giving pubs a motive to play and clans a reason not to rape them. Currently a smith and 2 serfs can completely restock a castle in 3 hours max, which makes civilian classes irrelevant.
2nd, find an effective way for them to know at least the basic rules of the server + tutorials on how things work. Most pubs dont even know this forum exists. I bet 90% of this forum's members are clan members or people who have formerly been in clans and will be again in the future.