[Simple Explaination and Tips for the Game]
1): Construction: The range of resources you can consume in a construction is 30 to 999.
The recipes arz Fuel/Ammo/Steel/Bauxite (aka FASB). However, do not waste too many resources on construction in the begining stage b/c you can get rare ships reward during the quest in future too. And as my experience in the Chinese Server, they will have some event for limited constrcuction. So you better save up some of you resources for events.
2): Modification: There are three features in modification: Enhancement, Modification and Skills. Personally, I think "Modification" is the most powerful features to power up you ships. Bascially, it is like the "Evolution features" in FGO and other games where you upgrade you ship from a lower rarity to a higher one. Although the modification will remove all the enhancement status of your ship, it is still more powerful b/c you ship will then start at a higher stats in all aspects.
3:) Affection: Each ship has a Affection level on their own, it's like the level of closure in a relationship, the higher the affection level, the higher the buff on your ship. In short, the affection start at 50 on each new ship. It will either increase/decrease. If the affection level in 50, no pros/cons will happen. But of the level is <50, the Accuracy/Evasion/Critical damage rate of the ship will -5%. If the level is >100, the Accuracy/Evasion/Critical damage rate of the ship will +5%. And if the level reach 200, the rates in those aspect will +20%! In order to maintain a high affection level, you need to give up if the battle is to hard and give you ships some "Damage Control". If you forcefully continue the battle, the affection level and the rate of critical hit will also reduce. More importantly, if your ship's HP is down to 0, the time that need for repairing your ships will doubled. So my advice is to stay safe and give up when neccessary.