From a direct game questing approach with a goal of mastering your pirate.
(im not a pvp'er)
I think your doing pretty good quest wise if your at/around 20%.
An hours or so work on those grenades at a quiet kingshead... and youll gain a notoriety level, and several grenade levels. But bring a friend for company, and to teleport back and forth for reloads
Other than that i'd say your doing fine. Your already on the right track planning to bring those lower level weapons up to speed. Work on evening up the weapons skills, and continue to mix a little leveling time amongst quest time. You still have weapon upgrade quests coming on the Cutlass, Pistol, Dagger, and Staff when you eventually get that. Also keep in mind when it comes to the boss battle at the end of the quest, Sailing and Cannon skills are paramount (unless you have someone else sail, in which case cannons would be key).