Active Time Battle System
While this is an adventure and the continuation of the story that was presented in XIII, it is also a fighting game that maintains the traditions and the level of concentration that the JRPG genre is so well known for -- and that being the case it is in your best interest to learn how the fighting system works, and get good at it.
While it is true that you can follow the tactics that are presented in this WTG up to a point, I honestly believe that doing so without understanding what they do detracts from your potential enjoyment of the game. Just because I chose to fight a battle the way I did does not mean that you must do so -- in many cases the choices that I made were not the only way that the battle could be fought, they were simply how I chose to fight it.
-- Understanding the limits on Attacks and Abilities --
When the game first begins you have three segments to your Action Time Battle System (from here on we abbreviate that to ATBS) -- these segments are basically power bars, which recharge over time and which dictate which and how many attacks or abilities you can take. While most attacks and abilities only use a single segment, some will use more -- and while you begin the game with three segments (which is what the enemies you will face have) you will eventually upgrade your ATBS Bank to a total of six (6) segments as the game progresses, which gives you something of an edge in battle.
Active Time Battle System Tutorial
The upgrades to the ATBS Bank are obtained in several ways -- two segments are obtained through choices that you make as you expand the Crystarium, and the third is obtained when you acquire an item that has the ATB 1 passive ability imbued in it.
At the bottom-left corner of the screen is your ATBS Gauge, which contains your ATSB Bank (segments), and below those the timer bar that must fill before you can use them. You have the choice of choosing the attacks and abilities that you use, or simply using the Auto Battle mode, and you can stack and activate the attacks immediately but they will not actually go into effect until the timer bar is fully charged. As you become more familiar with the different jobs, spells, and abilities you will start to develop your own preferred combinations, but for now you know what you need to about that.
Located in the upper-right corner of the screen is your Stagger Meter -- which naturally fills as you attack the enemy and, once it reaches the required percentage for that enemy, staggers them. You fill the meter by attacking, and magic-based attacks will fill it much faster than physical attacks -- though it should be noted that direct attacks decrease the rate at which the meter drains. There is actually an Achievements associated with staggering enemies, but it is not something you need to work towards as it will come naturally as you play, so do not worry about that.
-- Encounter Circles --
In the previous game battles generally took place when your character arrived at the static location of specific mobs, or at their current location, and battle commences. In XIII-2 it works a little different... While there are instances where you will do battle with the mobs at specific locations, battles can also happen randomly, using the Encounter Circle System -- which is a circle that appears on the ground that changes in color depending upon the circumstances.
When the circle is Blue it means that there is a distant enemy that you can do battle with if you want to, or you can head away from them to remove the circle and thus avoid the battle -- which you might want to do if you are not prepared or need to restock items. When the circle is Yellow it means that an enemy is nearby that wants to fight you -- and again the decision as to whether that is going to happen is mostly up to you. When the circle is Red however, it usually means that battle is imminent and the enemy is close by.
Once the battle commences a Mog Clock will appear on the screen at your feet that represents the three stages of battle -- Stage 1, the green stage, indicates that you can engage the enemy with a preemptive strike (and if you can you should). Stage 2, the yellow stage, indicates that the enemy is combat active and can attack you -- or rather can try to attack you -- you can still retreat from it at this point. Note that depending upon the speed rating of the enemy they may not have a green stage and so the battle will actually begin in Stage 2, which means you could not have launched a preemptive strike against them anyway.
The last stage is Stage 3, the red stage, when the Mog Clock Hand has swung around to the other side. At this point battle is imminent and there is no running away from it.
Remember to keep an eye out for the Cinematic Action Segment during boss battles, and to try to hit each button/action successfully, as that not only improves your damage on the boss but also counts for one of the Achievements/Trophies.