I love tucking my tops in my pants, I think that it gives the body shape also it looks smarter and elegant in my opinion.
A person can experiment with cardigans as well to give it that preppy chic or edgy look, it all depends on what style you are going for. This look doesn't work if you tucking in a very baggy shirt in because it will end you bulging and become very unflattering.
You can wear and type of pants, skirts and shorts as long as they are fitted and are not too baggy. Great look for any type of occasion.