You’ll start to notice improvements at around 100% Magic Find, and by 200-300% it will start to become less powerful. There is no cap on the magic find, but there are diminishing returns. When you insert these 7 perfect topazes you immediately get 168% MF. To do so you will need a 4 socket armour and a 3 socket helm. The easiest way to get more MF is to socket perfect topazes into Armor or Helm.
You need to stack much more MF to see that magic, rare, set, legendary items. While you play you will get such items as boots, gloves, accessories with magic find, but if you have 15%-30% MF it won’t make any particular change. You can get Magic Find on almost every type of equipment.