If I can give you a tip, try forging weapons with different command lines, different command lines give you access to different tech trees related to that specific command line.
To make an example, a sword with Read Blade has access to Double Mist>Roundabout>Bopeep, but a sword with a Blast line gets Noggin Knocker>Bear Slash>Vandalize, all weapons work like that, try forging things that have access to different basic lines and work your way up from there.
Martial Arts are a bit different though since they have unique weight mechanics in this game.
You have Lightweight, Medium and Heavy martial arts styles, whether a character falls into one of these three styles depends mostly on their weight, lightweight characters like Armic or Henri can very easily fit into the lightweight line but have troubles going for heavy style, while people like Anzan or Musol cannot go lower than Medium.
Midweights like Laura can effectively jump around between the three styles by adding or removing weight through equipment, which also factors in the total weight calculation for deciding which style they use.
On top of this, you can only use Heavy style MA if you have no related MA panel.
Then there's Roy, who is a metajoke on all of this, you'll understand once you play as Judy or Ruby.>but why does it effect NG+
Because in Unlimited you have ecology mechanics similar to Minstrel Song.
That means whatever you fight ends up making certain monster families weaker or stronger throughout the course of the game, and ecology history is one of the things that is carried over in NG cycles, which means on NG+ you start over with a non neutral ecology, which means it's a lot easier to get high rank monsters for certain families on normal encounters.