Late spring is when the tie waist dress starts earning its space on the rail, once the weather's warm enough to go bare legged but you still want something that does a bit of shaping for you, rather than a slip you have to hold in with a belt bought separately and usually left on the kitchen table on the way out the door. It carries you from a long lunch into an evening without any need to change, which matters more than people admit once you've got somewhere to be straight after work.
It's good for the in between occasions, a christening where you don't want to look like you tried too hard, a garden do, a work thing with wine involved. What it sits next to in your own wardrobe tends to be simple, a denim jacket for the walk there, flat sandals or a low block heel, a cardigan thrown over when the evening cools down, because the dress itself is already doing enough with that knot and the shape it creates, it doesn't need competing with. I made the mistake once of adding a statement necklace to one and ended up looking like I was wearing two outfits having an argument.
The difference between a tie waist dress that flatters and one that just sort of sits there is almost entirely in the tie itself and what's behind it. A proper one has enough fabric in the ties that they sit flat and tie into a knot with some body, not a thin strip that twists into a shoelace and digs in. The waist seam needs to actually be where your waist is, which sounds obvious until you try one on and find it hitting your ribs or your hips instead, and no amount of tying fixes a seam in the wrong place. Check what's happening at the back too, a lot of cheaper ones gape at the spine once you've cinched the front, because there's no shaping back there to hold it, just one long flat panel doing its best.
For colours, plain ones in a single shade are easier to live with long term than a busy print you'll tire of by August, though a small, repeating pattern in navy or a muted green hides the slight pull lines that tying always creates across the stomach. Block colours in deep red or bottle green photograph well and go from day into evening without a change of shoes.
Thrown over a plain white tee and worn open like a shirt dress, mine's turned into the thing that makes last year's trainers look like they were bought for exactly this.