I know all about being on a budget, so it's okay.

I let my standard sized chickens run the farm without barriers, I only have a top on my pens.
In all honesty, hawks have claimed 2 chickens, while owls have claimed 1. My biggest killer was the neighbor's pigs, once they left, my chickens stopped vanishing.
My point is, it's okay to save money and wait to buy a better top later.
Accidents can and will happen, but none of us are exactly bleeding money. So don't panic about buying tops ASAP, save your money and get something good when you can afford it.