Attack on Titan 2

As previously stated you shouldn't have to worry about this achievement; however, it is one you want to keep in the back of your mind. You'll start earning Wings of Freedom once you've been officially inducted into the Scout Regiment and you earn them by completing missions and other small tasks in Daily Life. Below I'll list what they're used for and specifically where you want to spend them and you can only hold 99 Wings of Freedom at any given time.

USED FOR

-Upgrading bases to use in battle
-Policies that give you benefits in battle and in Daily Life
-Training at the Training Field (tied to another achievement)

IN DEPTH

Training

Wings of Freedom are used at the Training Field once you gain access to training as you progress through the story. The 3 types of training are ODM Gear, Hand to Hand Combat, and Lecture. There is a separate achievement tied to the training to get maximum rank in all 3 sections. You can do Solo training or Join Training, with Joint Training potentially yielding better results. The more you train, the less likely you are to succeed and you can spend more Wings of Freedom to increase that chance. If you're just going for spending the Wings of Freedom you can always spend the maximum amount to make sure you'll succeed, or if you want just spend 1 in Joint Training. Spending 1 in Joint Training on all 3 section will increase your progress towards spending 1,000 Wings of Freedom; however, it'll also increase your progress towards maxing out all training. Even if you fail at a training section (which will happen the further into it you get) it'll still give you progress towards maxing it out so efficiently only using 1 Wing of Freedom is better than using the max allotted.

Upgrading Bases

Upgrading your bases is where the majority of where your Wings of Freedom will be spent. To be able to get all your bases to level 3, except the Attack on Base as that is restricted to a level 1 base, you will need to increase friendship with certain characters. Once certain characters get to higher ranks, Rank 5 and higher, you'll be able to start obtaining level 2 and level 3 bases. Characters such as Pyxis and Kitz will give you these options as well as other commanding officers through friendship.

Policies

The Policies are another way you'll be able to spend your Wings of Freedom and along with upgrading bases, most of your Wings will be spent here. Policies have certain benefits such as capturing a Titan easier, increasing the amount of Friendship you obtain with your allies, and increasing your experience gain. These policies range from 2-10 Wings of Freedom and you can only have one activated at a time. Purchasing a new policy will overwrite the previous one, going on a mission will use up the current one, and turning the game completely off will deactivate your current one making it useless.

So in detail those are all the ways you can spend your Wings of Freedom to get the Reformation achievement. One of those achievements you don't have to worry about too much, but it's also one you want to keep in the back on your mind. Before going out on the next mission maybe get a policy that will increase your XP gain, or maybe spend them at the training area to make your character stronger. Just remember once you get to 99 Wings of freedom you won't get any more until you spend them. If for some reason you've maxed out your character level, all your friendship, all 3 training sections, AND bought all level 2 and level 3 bases and still haven't obtained this achievement just buy different policies over and over again. This is a very confusing achievement once the game starts but once you're introduced to it throughout the game it makes total sense and is a very simple achievement.