like most i'm ws middle finger, a ring finger and d index finger
then it's pinky for shift and thumb on spacebar.
i also tend to try and standardise my in-game controls. tab is always inventory, mmb is always mellee, f is always special ability, g is always grenade, c is always toggle crouch with z being toggle prone if it's a seperate key required and v is always changing modes on weaponry (with t as changing optics, basically it's battlefield controls)
then normally i'll put primary and secondary on my forward/back mouse buttons then keep whatever gun i've set to the closest one (i have stubby cornish thumbs) as my shtf gun so in survival games it's the one i'll never use unless it's a pitched battle.
almost never use ctrl, unless it's unchangable.