You only need two days at Universal. It'll get boring after that.
You can save money by staying at Cabana Bay in one of the rooms with a kitchenette. We loved ours! We ate breakfast in so we could sleep a bit later and still have time to eat before getting to the parks when they open.
We drove so we brought food with us and then I did stop by the grocery to buy smores fixings rather than pay the hotel prices for marshmallows and graham crackers.

We roasted marshmallows at the fire pit.
The Trader Joes is not far and, of course, there's Publix and a nearby Whole Foods.
We stayed at Cabana Bay twice and loved all the pools and the lazy river. NOTE: They have added a hotel there but not increased the number of pools so it does get crowded!
I've stayed at another Universal hotel and like Cabana Bay the best. One drawback is that the check in is frequently slooooow.