to increase your weapon power level. There are 3 types of Modify which include increase Magazine Capacity, Penetration (increase headshot damage) and increase rate of fire.
increase the overall stats for that weapon. You can level up the weapon by using weapon growth cards which has different types that give different amounts of experience (S,M,L).
max level of your weapon, something more like a limit break in RPGs. There are two types of fusion which are either by firearms or by using fusion cards.
getting stronger weapons as much as you can for beginners because of higher grade and rarity of the weapon that gives the highest amount of weapon power when maxed level compared to lower grade and rarity of weapons.
time roll for Upscale because you will automatically obtain a 6-star weapon with a chance of getting grade A weapon which will help you a lot during the early game.