one thing you want to have in a fan is a high rotation/m (airflow, in cubic feet) and a low db (noise) At least stay under30 db, and for airflow, get at least a 30 CFM (cubic feet per minute)
now, ot make it cool, get an LED fan. LED fans has little light bulbs on them, but the whole fan gets illuminated. Even your OPC get colored, which it looks awsome. You can get some LED fans that changes color. (blue-red-red-yelloe-purpl...) ypu can get fans who stay the samr color. But whatever you choose, LED fans are great.
now, when oyu said, 'what other things that i can add to make my PC cool and run better.' you meant cool as cold or cool as nice stuff?
Cause, one thing that is cool, is neons, or LED lights. but it dosnt give you a better perfomance.
You can add more fans (LED) and that would make it cool (in both ways!) and you can also change the fans you have now (probably black ones!) into cool fans.
Hope this helped.