Firsly, each operative [will] have their own page on this site dedicated to them.
You can thus view each operatives page to see how to make that specific operative stronger.
This page is dedicated to explaining how to make operatives stronger in general:
Note that nothing on this page really matters for new players, and new players can safely ignore this page until they start to level up or struggle with fights.
The max level for players in SCZ is Level.100, and the max level for operatives is Level.80.
Getting an operative to max level [80] is by-far the easiest way of making them stronger.
Each operative uses a weapon of a specific type (Pistol, Assault Rifle, Sniper, Shotgun, etc.).
Much like operatives themselves, each weapon can go up to Level.80.
Getting your operatives weapon to Lvl.80 is one of the easiest ways of increasing their performance.
Weapons can be given "Parts" - attachments that add some stats to the weapon.
Generally speaking, you want all your operatives to just go for maximum ATK.
You unlock Parts from weapons either by
Getting specific 4* and 5* weapons to Lvl.50
Buying the Parts from the store for the current event
Buying the Parts from the general store
Weapons each have a "Tier".
The weapons effects get stronger the higher their tier.
To increase a weapons tier, you need to use a duplicate copy of that specific weapon.
4* weapons can go up to T5 - A4* weapon at T5 therefore requires 5 copies of that specific 4* weapon
5* weapons can go up to T2 - A 5* weapon at T2 therefore requires 2 copies of that specific 5* weapon.
Increasing the tier of a 5* weapon from T1 to T2 is always a large performance boost, whereas increasing the tier of a 4* weapon is usually relatively minor.
For many 4* weapons, going from T1 to T5 is a small boost - sometimes resulting in less than 10% overall performance difference to a strong operative.
SCZ has a lot of different weapons in it for operatives to use.
Each of these has different stats - damage, RoF, magazine capacity, as well as its unique effect.
This unique effect is the primary reason to choose a weapon, as it is usually a huge bonus to the effectiveness of the operative it was designed for.
The majority of 4* and 5* weapons, as well as all recent weapons in SCZ, are designed around a specific operative using them, and their buffs will improve one operative much more than all others.
It is often the case that the buffs given by a weapon can only actually be used by one operative, making the weapons effect essentially useless if used by other operatives.
New operatives will always have their own 4* and 5* weapon - these weapon will have been designed around them, and the weapons effects will affect the new operative much more than any other operative.
Operative-specific 4* and 5* weapons are often called  "signature", "specific", or "event" weapons, or similar.
As such, for all new operatives you should only ever consider using their signature 4* and 5* weapons - in terms of their performance nothing else will ever compare.
This site has articles on each operative - these articles will state what that operatives specific 4* and 5* weapons are.
Given how much their designated weapons outperform everything else, there isn't really much of a reason to ever consider using anything else, and I usually don't list other weapon options for new operatives, just because nothing else will come close to their designated 4* or 5*.
The 4* weapon for the newest operative is very easy to get - you can just buy it from the event store. The first copy is half the price too.
(Buying the first copy of a new operatives signature 4* weapon in the event store cost 1.25 days of event currency [150].)
If you didn't get an operatives 4* weapon from their event, you can get it by buying it from the (Shop -> Circulation Hub -> Fortune Weapon Exchange) section of the store.
You get the currency needed to buy items from that part of the store by doing the "Arms Hub" operation (accessed via Fight -> Operation -> Arms Hub)
This is a less efficiency way of getting 4* event weapons - it's cheaper to buy them in the event store, so always pick up the 4* for the events new operative in the event store whilst it's cheap.
Each character can have three logistics officers assigned to them.
Each logistics officer provides certain stats to the operative they are assigned to.
Each logistics officer is either an Intelligence, Medical, or Material officer (a.k.a. "Left", "Middle", "Right").
Each operative can have one of each of these.
Each logistics officer can be levelled up to Lvl.15. The higher the level of a logistics officer, the higher the stats they provide.
At Lvl.15, the stats provided are:
Intelligence - 50 DEF 98 ATK 20% Max HP Boost
Medical - 50 DEF 1,492 Max HP 20% ATK Boost
Material - 98 ATK 1,492 Max HP 20% DEF Boost
For a max level (Lvl.15) officer the percentage boost is always 20%, but the flat bonus can vary by a few points (e.g. 98 or 101 ATK instead of 100)
Each officer always gets the same stats (E.g. Cammellia [the Material Officer] of Couplet squad is always 101 ATK - every Camellia is always 101 ATK.)
Each logistics officer is part of a squad.
If an operative has 2 or 3 officers from the same squad equipped, then they get the 2/3 and 3/3 bonuses for that squad, respectively.
Each squad has its own distinct name (E.g. Couplet, Zephyr, Aileron, Vector, Lux, etc.) making it easy to figure out if two officers are part of the same squad.
These squad bonuses are usually both very strong, and also specific to a specific character.
Each new operative will have a squad introduced alongside them. Their designated squad will generally only buff that new operative, or will provide such specific buffs that no other operative gets much benefit from using them.
As such, each operative tends to have one logistics squad that provides them with much more performance than other squads, and you generally only want to use the operatives designated squad.
The logistics officers for the new operative can be bought in the event store during that new operatives release event, making it very easy to get them.
If you want to get specific logistics officers for an old character, go to (Fight -> Operation -> Mind Refinement).
You can use Presence in order to clear the mission to get the Elite Personnel Limit currency item.
You can use these to buy the logistics officers you want from (Shop -> Circulation -> Elite Logistics Officers)
Clearing Mind Refinement does also give you a random officer for a specific squad (shown in the bottom-left of the Mind Refinement interface).
Since which officer you get is random, this can take a lot of Presence to get a full squad via this alone.
Generally speaking, it is more efficient to just buy the officers from the event store during a characters initial release, and you are generally better off focusing on easily getting the logistics officers for the new character rather than inefficiently getting the logistics officers for older characters.
See each operatives specific page to see which squad they want.
(This is usually obvious from the squads buffs - characters are often explicitly mentioned by name. If not, the buffs are so specific it can't be anybody else)
Each logistics officer has three "Talents" - stats they provide to their equipping operative.
These stats are randomly determined upon acquiring the logistics officer, and are random every time - if you buy multiple copies of a specific logistics officer, then each one will have different talents, randomly determined each time.
The first two talents are "Basic" talents.
The third is the "Special" talent.
One Basic talent can be re-rolled using the "Revision Limit" currency - re-rolling one basic talent locks the other basic talent such that it can never be altered.
The Special talent can be re-rolled using the "Revision Application" currency.
Ideally, you want your logistics officers to have three perfect talents, however since you can only re-roll two of them, this means that not every logistics officer can be made perfect.
Instead, a logistics officer can only be upgraded to have three perfect stats if they already have one basic talent upon purchase.
If a logistics officer has one perfect basic talent, then you can re-roll the other basic talent, locking the perfect one, and then re-roll the other basic talent as well as the special talents to perfect, thus getting a perfect logistics officer.
It is thus recommended that you buy logistics officers for new characters until you get one that has a perfect basic talent, as then they will be able to become perfect.
Experienced players often use a very large percentage of their event currency buying logistics officers in order to get one that has a perfect basic talent.
If a logistics officer doesn't have a perfect basic talent, then do not waste any resources on re-rolling them - they can never become perfect, and hence you will eventually replace them with a better (perfect) officer, so don't bother re-rolling any logistics officer unless they already have one perfect basic talent, and can thus become perfect.
Re-rolling a talent is simply a random roll - you can choose to keep the existing roll or swap to the new random roll.
If you do enough normal re-rolls, you can get a Targeted re-roll. This limits the re-roll to only one specific stat.
The sheer number of possible rolls means that getting a perfect re-roll is extremely unlikely, and even Targeted re-rolls are still highly unlikely to be perfect.
In all my time playing Snowbreak, the total number of Logistics Officers I have managed to upgrade to be literally perfect is 1.
Don't worry about getting them literally perfect - You might get lucky once or twice, but getting lots of logistics officers to perfect is a fools errand.
Instead, getting lots of logistics officers to good rolls is a much better use of resources than trying to get 1 perfect.
Possible Talents
Basic Talents
Max HP 4.0% 5.5% 7.0% 8.5% 10.0%
ATK 4.0% 5.5% 7.0% 8.5% 10.0%
DEF 4.0% 5.5% 7.0% 8.5% 10.0%
Crit DMG Amplifier 4.2% 5.8% 7.4% 9.0% 10.6%
Shooting Crit Rate 2.1% 2.9% 3.7% 4.5% 5.3%
Skill Haste 7.7 10.6 13.5 16.4 19.3
Alignment Index 42.4 58.3 74.2 90.1 106
S-Energy Recovery Bonus 5.6% 7.8% 9.9% 12.0% 14.1%
U-Energy Recovery 5.6% 7.8% 9.9% 12.0% 14.1%
Special Talents
Kinetic DMG 3.4% 4.7% 5.9% 7.2% 8.5%
Thermal DMG 3.4% 4.7% 5.9% 7.2% 8.5%
Frost DMG 3.4% 4.7% 5.9% 7.2% 8.5%
Electrical DMG 3.4% 4.7% 5.9% 7.2% 8.5%
Chaos DMG 3.4% 4.7% 5.9% 7.2% 8.5%
Healing Bonus 4.2% 5.8% 7.4% 9.0% 10.6% Note that this means healing applied, not healing received.
Auxiliary Units Strength 4.2% 5.8% 7.4% 9.0% 10.6%
Shield Construction Efficiency 4.2% 5.8% 7.4% 9.0% 10.6%