I love shopping SheInside for swim because in reality, a swimsuit is going to be relatively worn through after a few summers. I would rather spend high dollars on a nice coat or pair of shoes before a swimsuit.
SheInside has been the haven for everything affordable swim. You have to be cautious when looking at size charts on this site though -- just make sure to give it a glance before checking out. The top and bottom are oftentimes sold together so you'll get a top and bottom in a size medium. My hips and chest are two different sizes which makes shopping this site finicky. Each item has it's own individual size charts, so those are your ticket to finding a suit that properly fits.
This high-waisted polka dot swimsuit from SheInside has been a summer favorite of mine. I feel comfortable in high waisted bottoms and the top has shoulder straps, which are a must for me. The top is also padded and who can pass up a cute polka dot print?!