If you've never played the Yakuza Series, then you might be taken back by just how many different Stats and Skills you will be able to use the EXP you earn on. Because there are literally tons of different things to spend you EXP on, you will want to earn as much EXP as you possibly can as quickly can. In hopes of doing that very thing, you should always think about unlocking the experience boosting skills before doing anything else in regards to your Stats. In order to find where these given skills are, you will need to look under the Other Tab in your Stats Menu to see the four different tiers of each type of experience.
Since these Skills serve such an important purpose at the beginning of the game, it is recommended to unlock them as early as you can within the game so they can begin to help boost the EXP you will earn for the rest of the Main Story. On top of this, you can even get certain skills that will further boost the amount of EXP you earn simply by eating! These skills won't make as big on an impact should you wait to unlock them later in the Main Story, so definitely do so on the double after beginning the game.