To be a pro at the game you need only 2 operators
For attackers:
Ash - Can't die from a headshot, has the hitbox of a stick man, has a gun with decent controllable recoil and good fire rate
IQ - My favourite operator, Can see Kapkan traps and most other electrical traps including the bomb.
For defenders:
Kapkan - Amazingly good SMG, no recoil, great sight (reflex), fast fire rate, 2 armour, 2 speed, has amazing trip wires that blow people to bits
Valkerie Or Ela - Ela has 41 bullets that shoot faster than the sound of light, she is 3 speed 1 armour which means bullets won't hit her, shes super OP, that's why all the try hard shit players play her, takes no skill. Valkerie can deploy camera's to hard to reach areas which is beneficial to your team in Ranked. Her SMG is decent.
Generally if i defend i normally Main rook because of the MP5, it's OP with an Acog, plus you can deploy armour.