The print is the first thing to go, not the shape. You can tell a lot about a graphic tee by how it looks after the tenth wash, not the first wear, because the cotton can still feel fine while the design underneath has cracked or faded to half its depth. Mine tend to announce themselves as a bad buy weeks in, not on the day I bought them, which is annoying when you've already built outfits around them.
Keep it away from busy bottoms. A graphic tee wants a plain skirt, plain trousers, a denim that isn't doing anything loud, because one statement at a time is plenty and two patterns fighting for attention just looks like laundry day went wrong. For colours, I've had the best luck with washed black, a soft navy, or an off white rather than bright white, which shows every mark and goes grey faster than you'd like. A faded, slightly chalky print sits better long term than a glossy, new looking one, oddly enough, because the shine is usually the first thing to flake. In the shop, stretch the print gently between your fingers, not hard, just enough to see if it's bonded into the fabric or sitting on top like a sticker. Check the side seams too, a lot of cheaper tees are cut narrow through the body and then stretch out of shape within a month, so you end up with something baggy in the wrong places and still tight across the shoulders. Hold it up to the light as well, since a lot of graphic tees are printed on thinner cotton to keep costs down, and thin cotton over a bold print can go slightly see through under certain lights, which nobody tells you until you're stood under one. A well made one has a slight weight to the fabric, a print that sits flush rather than raised and shiny, and a neckband that doesn't go slack by the second wear. The disappointing ones feel fine on the hanger and then lose their shape the moment they meet a radiator or a tumble dryer, which is really a fabric problem dressed up as a care label problem.
I wear mine with a plain midi skirt and trainers more than anything else, because the tee carries the whole outfit and I don't have to think past it. One honest find, a longline graphic tee with sleeves that actually reached my wrist straight off the rail, no layering, no adjusting. Small thing, but I still think about it.
It turns the plainest bottom half you own into an outfit that looks like you meant it.