Today's Monday... where the heck is my SC5? T^T *inhale,exhale,inhale,inhale,inhale,EXHALE* Phew! O_o you guys must be having fun with the game :) Fret not! I will catch up soon!
Basically you earn player points for playing in modes like Story, Arcade, Quick battle and Legendary Souls, be it win or loss. Of course, winning gives you more points than losing. The higher your rank the more points will be needed for lvling up, and you'll unlock some cool stuff as you level. Such as CAS equips. and weapons too
Actually difficulty of Arcade doesnt affect number of player points gotten iirc. You can set difficulty to Easy Normal or Hard. If you wanna rush, go Easy and crush Arcade Mode and get tons of pts. lol