Unfortunately here in Italy we don't have Thanksgiving Day but I would like to celebrate it. Not because I'm a really religious person but because I think that in our everyday life we have so many thing for which we should say "thank you" and most of the time we forgot it. So in every country there should be a festivity to rember this, maybe not related with religion. Anyway, I think that dress up of Thanksgiving is just like dress up for the Christmas' lunch. You should be comfy but also chic and a little bit "formal". I would probably choose a dress or a simple sweater of a good quality. There are many sites from which you can have some inspirations. For example, if you go to https://www.stylewe.com you can find an entire part of the site dedicated to this celebration. You can find it shopping at thanksgivind day and see that there are lots of dresses, jumpers and skirts appropriate for the occasion but also many accessories to complete your outfit. Another idea, as you know that I love them, it could be to wear an overall for women, so that it can be even more easy to build the perfect outfit. I leave you some images taken from the site from which you can be inspired down below, I hope you'll like them.