Whatever you wore before surgery, you can wear afterward with very few exceptions. Many pouching systems are made today that are unnoticeable even when wearing the most stylish, form fitting clothing for men and women.
Depending on your stoma location you might find belts uncomfortable or restrictive. Some people choose to wear higher or looser waistbands on trousers and skirts.
Cotton knit or stretch underpants or panty hose may give the support and security you need. Some men finds that jockey type shorts help support the pouch.
Women may want to choose a swimsuit that has a lining to provide a smoother profile. Stretch panties (with lycra) can be also be worn under a swimsuit to add support and smooth out any bulges or outlines. Men may prefer to wear a tank shirt and trunks if the stoma is above the belt line.