Cheaper tickets for Universal admission?

It’s my 2nd time going to Universal, so I am not sure how the fees work. I was planning to go to only Islands of Adventure for one day, and the other is just for city walk. I am going around the time of March, are there any discounts I can receive or website suggestions for cheaper tickets? It is 4 adults in total, and I’m going 2-3 days before my bday. Thanks!