Packing?

I am going on a week trip to Disney this summer, and after that a month in Oklahoma. Me being the over prepared freak that I am want to make a packing list a month ahead. For those of you who do not know both Oklahoma and Florida in the summer are very hot. As an added bonus I am only able to bring ONE PERSONAL ITEM!!!! So any packing tips or useful 1 month packing lists (with amounts of specific clothing) would be GREATLY APPRECIATED! Thank you. 😓😶🤗🙏