Unlock All Unlockables:
If you press L1 + L2 + R1 + R2 at the same time you will be able to unlock ALL of the game's music, costumes, Story mode progress, movies, and more. If you have entered the code correctly the game will indicate that it is saving your progress.
Consider spending time in the training mode to hone your fighting skills before you enter into actual combat with an opponent.
You will only be able to go so far in the game by mashing buttons, if you have aspirations of becoming proficient at fighting you have no option other than to learn combos.
If you are new to the game you will find trying to memorise the different combos daunting. To begin with just commit to memorising a few simple ones and work your way up from there.
You will find that you will have more freedom to follow up with attacks/counters if you use directional inputs for blocking instead of buttons.
OMG Breast Motion:
Losing with 10 female characters in Solo Vs mode and watching all 10 losing cinematics will unlock this feature.
At the 'Options' menu press LB + LT + RB + RT to unlock costumes, Story mode progress, system voices, music, and some movies. If you have entered the code correctly you will hear a confirmation sound. Entering this code will not unlock the victory and defeat movies for Raidou or Marie Rose, or any DLC costumes.