I kept playing Thracia while Project Exile worked on the translation, and finished it on the weekend the final version came out. Have to say, completing Thracia was a struggle and this game made me uncomfortable more that any other Fire Emblem games. There are a lot of things the game throws at you, and you need to be ready for it. Here's a list of tips I'd give to anyone who also found themselves under the pressure.
Capture is a big mechanic in the game. Once you captured an enemy, you can steal all their equipment before releasing them, giving you some much needed equipment. It's easier to get some equipment early on this way, but better equipment comes in later chapters. However the enemy can also capture your units who can't fight back, and when they do they automatically steal all their equipment, except scrolls and personal weapons. This can be used for capture baiting, but the game is possible to beat without it.
Status effects like Sleep, Silence and Berserk last until the end of the chapter, no X turn duration, very powerful effect. Advised to steal these whenever you can, since the enemies don't have Restore staves most of the time. Having your units under status effects can be very annoying.
Boss tiles give much higher defense and avoid bonuses. This only boosts defense against physical attacks though, so mages and magic swords can be much more effective. They also block you from using status staves on the bosses.
You'll run into escape chapters. Make sure Leif escapes last, otherwise anyone who left on the map is automatically captured. This can make your runs impossible in some cases.
Fog of War is bad. The only way to see more through this is if you use Torches. Most Gaiden chapters have this, other than that only Chapter 12 gives you that. This makes the formation screen a big black screen as preview, so if you don't like that, check out the maps on fireemblemwod.
You can't change the positions in formation. You should also check the deployment order on the maps on fireemblemwod if they give you problem. Early maps usually put the army in one spot, but later maps they split them up, and some cases leave you with groups next to a door they cannot open.
Fatigue is also a big part in formation. The only way to reduce it to 0 is if your units skips a chapter or you give them an S Drink - that is why it's good to have more healers/boss killers in your army.
Some units can ride horses, but indoors they need to get off from their mount. Unfortunately some units have different weapon ranks when they are mounted and when they are not, and most lance weapon ranks are only on mounts, except for Dalshin who might not be used in the long run.
Ballistas are no joke, they have good hit rate and damage a lot. In Chapter 14 you might want to take them out with Olwen and a Bolting tome, assuming she got the weapon ranks to use it at the time. Makes the chapter much more manageable.
Leadership stars boost every units hit/avoid rate by 3% in the army. Saias has 10 leadership stars, so you know it's bad when he's around. You can use hit/avoid rate boost as well, including leadership stars, Charisma skill and Supports. Kingmaker is a weapon that gives the Charisma skill, it's best used with Leif who supports a lot of units. To see who supports who, check out the picture below. Keep in mind that even with a lot of support the minimum and maximum hit rates are still 1/99%
Movement stars give 5% chance to act again. They are very useful, but try not to rely on them too much in your main strategy. It just makes the game more annoying when it makes the enemy act again.
Staves can miss, even the healing ones. A healer with high Skl will not miss, but they can also cast the heal twice on the same target. Sometimes the enemy gets into this too, but don't rely on that.
Scrolls will boost the growth rates of the unit who have them in their inventory, and when they have multiple, they stack together. However units with scrolls won't get critical hits on them, so it's better to give them to multiple units. Check out the main site for the bonuses they give in growths, but Exile patch already have them included for you.
Each unit has a hidden PCC stat, which is a multiplier on their critical value when they do a follow-up attack - a unit with high PCC will usually get a guaranteed critical on the 2nd attack, making it a much valuable stat. For this early on Othin with Bhuj, Fergus with Brave Sword, Olwen with Dire Thunder or Mareeta with her personal sword can get you some easy kills.
Your company is separated at the end of chapter 3, and they will return later with the equipment you left on them. 13 items from Leif's and Lifis's equipment will be stored in Chapter 4 chests and Eyvel's inventory goes to the storage. Marty won't be able to attack you in Chapter 8 if you don't leave an axe on him. Tanya and Dagda needs weapons, vulneraries and a Torch with them. You could bring the Brave Axe with Leif to make Dalshin more useful in the upcoming chapters.
Lifis can easily steal magic tomes early in the game, making the mages go running away from the map after that.
Gomez is probably the nastiest boss early on. Make sure you have a few uses on the Grafcalibur to deal with him. If you met Henning in FE6 8x, Gomez is the same, but much more difficult.
You want Safy to reach A rank of Staves by Chapter 12. Not getting A staves will make the upcoming chapters more difficult without warp staves. Keep her using staves or promote her if you can.
Try to capture Salem early on in Chapter 12. He unlocks Chapter 12x for you and the Sleep staff on him is very valuable later on.
Lara is the only dancer in the game, and she promotes into that class in Chapter 12x. Make sure you warp her next to Pahn to talk to him, then steal the Thief staff from Tina - the only Thief staff in the game which you want.
Save some door keys. Some late chapters will require door keys from you, including the final chapter with 6 locked doors.
Try to use as many units as you can. Until you have a better sized army, it's good to make the most use of them. If someone gets really good, use them. Mekkah made a pretty reliable tier list regarding that. Still, I ended up with a Tanya who got blessed with movement and speed, and I liked deploying her because she supported with Othin. Mareeta was my boss killer after Asvel, I used the Paragon Sword with her instead of Carrion.
Make sure you have one of your units captured by Chapter 21. Chapter 21x is the only gaiden chapter without fog of war and it only unlocks if somebody is captured. It has a lot of useful staves for the late chapters.
Skills are very useful. For example Wrath gives you guaranteed critical on counterattack with Othin or Brighton. For a long time Nanna will be your only unit with Charisma. Nihil can negate all skills on bosses. Paragon makes you grow like weed. And don't get me started on praising Astra.
Magic and Resistance is the same stat, making Ensorcel staff twice as good for you. You can go above 20 Mag to cast status staves on enemy units.