i'm right handed, my dad was left handed and i grew up using the computer with his setup, so i game left-handed. my keybinds are usually pretty similar, IJKL movement, P reload, N sprint, SPACE jump, ;'/[] as little finger keys so stuff like crouch, select item etc.
the only difference is with WoW, where i'll move the entire keyboard to the right so i can use WASD for movement and everything else for abilities, but that's only because Ctrl and Shift are easy key modifiers for my thumb.
if a game doesn't have rebindable keys i'll use external software to do it, or just not play. that shit should be standard by now
edit: as for mouse setup, i use a lefthanded deathadder, but my clicking remains normal, so left click with middle finger and right with my index... i'll admit, that part is weird, but it means i can easily adapt to regular setups by just moving the mouse