>>10910666expanding on this advice: dress for your body type as well! if you're busty or broad shouldered, you need more poof to avoid looking top heavy. you'll probably need a longer bodice unless you're very short, because using up all the horizontal stretch can take away from the length, as can a larger bust, and high waists can be really unflattering if you're fat. same goes for skirt length-- the dress may "fit" but be far too short on you, which makes it look ill fitted. i see that issue with sweets a lot. shapewear and corset undergarments can help with bunching and rolling and help give a defined waist, which is a big thing that can help the coord not look sloppy. pay attention to the straps on JSKs. if the straps are too short, it'll make the rest of the bodice fit badly as well. it's not hard to move strap buttons down on most pieces. socks are another common issue-- if the pattern is completely distorted, they're too small. tops rolling or squeezing can't always be avoided, but you can minimise it with glue or garters. i recommend pairing socks that roll or squeeze with skirts long enough to hide the tops. i also agree quality matters. thinner fabrics and poor construction will put a huge spotlight on any fit issues. in particular people tend to skimp on blouses. a cheap blouse will cheapen any coord.
finally: iron your clothes. it makes a massive difference.