To start with, find someone who wears close to your size and ask them where they do their shopping. My personal experience is that you really need to make the time to find a couple of stores that carry the kind of clothing you prefer - Florida for me was tricky, because of the heat and how everyone dresses was foreign to me. I used to dress a lot more conservative - now I just wear my shorts and tank top like all the other old ladies around here:)
It takes time to find the right store for you, my friends are all tiny whereas I wear a size 14, size 12 on a good day - it seems they cut off at size 12 at many of the stores, grrr.
Goodwill and tons of thrift stores abound in Florida - but I never buy my clothes there, simply because there are so many ladies clothing stores with deep discounts for all of ten bucks more. Ross, Marshals and TJMaxx are all over the place and have nice clothes and great discounts all the time - not to mention they do have clearance racks too.
There are a fair amount of consignment stores around as well.
Bealls is a Florida chain and has both regular stores with great clearance sales and their own Bealls outlet too. All their clothing is Florida friendly. Walmart around here is dirt cheap and they have a great selection in all sizes - but I boycott them for personal reasons, so I don't shop there.
Check out Catherines and Lane Bryant - my DIL likes them and they only carry larger sizes - good clearance sales on occasion.
I do like to shop at Dillards, considered a bit upscale - but I tell you their clearance sales are better than Marshals any day - because not only do you get a good deal $ wise, but the quality is there too. Even Macy's has surprised me with deep discounts.
Sometimes buying cheap means poor quality and in a short time you have to replace, so you haven't really scored.