A beautiful thing is not perfect —Anonymous
Tailor your trousers
and skirts so they fit snugly on your natural waist or hip bones
Shirts tend to come untucked or billow up because the waistband on your skirts or trousers are too loose, which allows for a shirt to come untucked because a) there’s a large gap and/or b) because the waistband of your skirt or trousers is sliding up and down.
If that’s the case, get yourself a good tailor. Seriously, it’s one of the best things you can do for your appearance. Your skirts will stay put if you tailor them to cinch at your natural waist and graduate out towards your hips; rectangular or tubed-shaped skirts will simply ride up and down.
Trousers and jeans you’ll want to tailor at your natural waist (if they’re high-waisted) or your hips (if they are mid/low) — a belt will keep them extra snug.