If you want more people to optionally pvp then you need to improve the pvp itself rather than offer more incentives.
It doesn’t matter how much more xp, gold or whatever you offer, people won’t flag if the pvp is bad, unbalanced or unenjoyable.
Work on getting the changes needed to improve the pvp system.
For starters steps need to be taken to reduce or outright remove the zerg fest that world pvp always ends up becoming.
Then you need systems in place to stop grieving, ganking and just outright toxic gameplay.
Next you need to make sure low level characters have a somewhat even playing field.
The entire war system needs a look at also as you’ve got next to no chance in getting into one unless your in one of the involved companies or being a friend of the guilds.
In short fix the pvp instead of trying to force people into an unenjoyable environment.