You can use an all day pass on the bus for 4,50$.
On food, the best and cheapest places are Burguer King, la lechonera, cuban café and supermarkets like Aldi, la chiquita or Fancy fruits.
For a place to stay in, i use Airbnb but if you don't feel comfortable using an app, you can check for hotels outside downtown disney and you will find rooms from 20$ to whatever the price you need.