Poly and mono are both unsaturated and they are healthier than saturated fats. Saturated fats should be kept below 10% of your total fat intake and come from animal products (meat, butter, eggs) and some vegetable products (coconut oil, palm oil). Most vegetable oils are unsaturated and the sources elce5c listed are all good sources. But let's not forget my favorite, avocados!
You don't need to cut out saturated fats completely (since you can't even eat a chicken breast without getting some), but you should always include good fats as well.