Avoid Loud/Noisy patterns, the simpler the shirt the better. Elegant, Sophisticated colours and classics, nothing shiny nothing patterned. Try to avoid shirts with plackets they look cheap and rubbish
Colours to look for if you're going with navy blue trousers are light to medium blues and whites. If you're going with beige, all blues light or dark, classic black or whites but my preference is blues as it's by far the most elegant combination and looks very sharp/expensive
Get an elegant brown belt, the more understated the better.