Ruffles catch the wind, catch on car doors, and catch every bit of spilled sauce at a table before anything else does. Worth knowing before you buy. They are also one of the few details that can make a plain dress look like someone made an effort, without you actually doing much at all.
Keep the rest of the outfit quiet. A ruffle dress with a busy print, a chunky statement necklace, or shoes with their own hardware and buckles starts to look like an argument rather than an outfit. Plain sandals, a simple bag, small earrings, that's it. The dress is already doing the talking, and a cheap ruffle in particular needs the calm around it, because the ruffle itself can look a bit flat and papery if the fabric's thin, and then it's competing with everything else for attention it can't win. A good one, cut with a bit of weight and movement in the fabric, holds its shape and doesn't need the rescue.
On fit, the main thing to watch is where the ruffle sits on your body, not just the dress size. A tiered ruffle skirt can add visual width exactly where you don't want it if the tiers start too high on the hip, so check where the first layer falls before you commit. Ruffle sleeves are the other trap, they look lovely standing still and can swing into a glass of wine or catch on a door handle the second you're actually moving, so if you're wearing it somewhere with a lot of standing and mingling, go for a dress with the ruffle lower down, on the hem or the neckline, rather than the arms. Go up a size if you're between, because a ruffle that's stretched tight loses its bounce and just looks like fabric trying to escape. The cheap version usually gives itself away in the finish, a ruffle edge that's been cut and left raw rather than properly hemmed, which fluffs and frays after one wash. A better made one keeps its edge and its shape wash after wash, and that's really the whole difference in price justified in one detail.
It's the wrong choice for anything that needs you moving fast, lifting things, or sitting at a desk all day, ruffles and office chairs do not get on, and for very formal occasions where the fussiness can read as try hard rather than polished.
Best suited to someone wanting a dress that does the dressing up for her, for an afternoon or evening where standing around looking good is most of the job.