Yes, you really need a greenhouse plastic. I have a neighbor who keeps trying to save money. He replaces his plastic once a year! All that work and it rips in the wind, etc. Congrats on your new greenhouse!
Our first plastic we actually left on our greenhouse for 7 years. That is longer than recommended but for all that work and time, plus inflation, we saved a lot by not attempting to use the heaviest duty plastic from Lowes. I recommend Grower’s Solution and Farmer’s Friend. They both are outstanding to deal with! I am sure there are others that are equally good, but that is where our experience is.