Now all this discussion in regards to these topics would be incomplete without touching upon the subject of modesty.
The scriptures are quite vague upon the subject of dress. The reasons for this are largely because the laws and commandments are like training wheels. They are not meant as a strict set of rules to abide by, but rather as a set of principles that once learned teach us how to make intelligent choices. So laying out a strict dress code defeats this lesson.
Modesty is a principle. We are taught to be clean, chaste, and virtuous. This includes how we behave and how we dress. Outward appearances are not everything, but they often reveal what is in our hearts.
When a young man dresses like the world, he will by nature and natural consequence, attract certain kinds of friends, including certain kinds of girls. These friends are by nature peers. And they will affect how we think and act. This in turn can sculpt our lives. And the same rules will dictate that certain appearances will also repel certain kinds of people too, including girls. Likewise with the girls. If they dress a certain way, they will by natural principles find themselves surrounded by certain kinds of friends, and will repel others.
If a young girl wears heavy makeup and skimpy clothes or the latest fashion she will attract the attention of those who find that kind of thing appealing. And the boys who are interested in virtuous girls may think that a girl that is dressed that way is a tramp and will look elsewhere for a suitable companion. If a young man wears baggy pants and the trendy clothing, he will attract the shallow and vain people, and a good girl will be inclined to think that young boy is not suitable husband material.
Modesty goes beyond how revealing clothing might be as well. Apparel that is excessively fancy or expensive attracts or repels certain types of people because it broadcasts what our hearts are set upon. It shows we want to be popular among certain peers. We should wear conservative styles because it reflects that we are disciplined and restrained in our habits.
A saying goes, that you can't judge a book by its cover. That may be true, but the cover does usually indicate the contents. And while you could also have the proverbial wolf in sheep's clothing, the initial appearance is often fairly accurate. And conversely, you can send a negative message by the clothing you wear. Now a counter this is that it's what is in the inside that counts. Again, that is true, but often what's in the inside is shown by the choices we make.
If you wear good, clean, modest clothing that covers your body and give you a pleasant appearance, it reflects upon who you are. And it doesn't matter what is popular, you will ultimately be happier as a person if you hold to your values.