I always say sunscreen on your face, neck and decolletage , every day, without fail - as that are the areas most susceptible to sun damage. Putting aside the fact it will make a world of difference to your skin in 10-20 years time and you’re protecting against cancers, right now sunscreen applied every day will refine pores and boost moisture. UV rays do all kinds of damage, and applying sunscreen even if you’re only outside for 10 or so minutes can help you avoid so much of it.
As for the rest of your body, I tend to judge that by what clothes are being worn and what skin is exposed. If you’re going to the shops in jeans + a shirt, you don’t really have to worry. But if you’re going out in shorts and a singlet top to a park or something similar, definitely apply it.
I think most of them can look really pretty, and on any shape they tend to create the illusion of a slightly more nipped-in waist, which is always flattering :)