IIR = Increased Item Rarity
IIQ = Increased Item Quality
These modifiers often show up on items, but you'll likely discard those items unless they fit into what you need for sockets and mods that help you stay alive.
Later in the game your first source of "MFing" (magic find) is to get a IIR and IIQ gem hooked up to bear trap (or anything else you prefer to attack with) and culling strike (ensures your last hit linked to the IIR & IIQ gems is with the attack you have culling strike on). Culling Strike kills an enemy on hit when they have 10% or less life left. As you can imagine, this is a nice way to drop a boss towards the end of their life.
When you find yourself overpowered in later parts of the game, try substituting gear that you don't rely on for sockets. Like your rings and amulets. Assuming you've been keeping your eye out for rings with a nice IIR and IIQ role. You'll definitely notice a difference in the items that are dropped.
While Witch Summoner (SpectreMancer Witch) doesn't have great longevity for game play in end game, they offer one of the easiest play styles that allows the greatest leverage to Magic Find With. You can use the attack/culling strike method mentioned above or if you get a powerful specters that shoot projectiles with the (raise specter gem) then you can hook them up with the IIR/IIQ gem combo and have yourself a nice walk in the park.