According to this link http://www.mousesavers.com/universalorlando.html, a 1 day/1 park ticket at the gate will run around $70! Ouch! I'd go ahead and buy the 1 day/2 park ticket on Universal's website for $73. After you are done with IOA, hop over to USF and do the Mummy and the Nuthouse coaster for the credits!
If you're going more days, look into the 7 day pass for $85.