As for any basic piece, a jean must be perfectly at your size: tight at the level of the thighs, and this whatever the type of jean. The break of the jeans must systematically be done at the level of the ankle, never before, otherwise it means that the jeans are too long. Similarly, if there is no break, your jeans are too short (but you should notice this easily). As a confirmation for the width of your jeans, try to grab them when you are standing, if you can't take more than a few millimeters between your fingers, they are your size. On the other hand, if you can't get into them, look no further: they are most likely too small.
Maintenance of the jeans
Ideally, you should wait six months before washing your jeans for the first time. No! Don't look so shocked. When you buy them, your jeans are just a piece of fabric. The longer you wait to wash them, the more they'll get used to your body (especially on your thighs). Then, wash them once every two months, no more. In the meantime, air it out regularly and store it on a clip hanger: never fold it in the closet, and remove visible stains with a brush, moistened if necessary. Why do this? Because the more you wash your jeans, the more they will fade and become rough. I also advise you to prefer hand washing, your jeans will suffer less. The average life of a pair of jeans if washed once a week in the machine is 6 months maximum. I've never been masochistic enough to try this with a 500€ Armani, if you have done the experiment, send me an email.
The shirt
I don't think it's necessary to point this out to you, but the shirt is still the most important part of any modern man's outfit (seductive or not). After 20, you can't expect to look serious wearing only T-shirts.
The cuts
Have-good-style-cuts-dresses
If you have to remember only one word when choosing your shirt, it has to be this one: fitted. A fitted shirt is a shirt that follows the curves of your body. Tucked into your pants, a shirt should not flutter at all. Note that if you are a little strong (meaning that you are a little overweight), prefer the straight shirt. Ideally, you should be slim, but this is also where a little rethinking can take place.
Manufacturers who offer custom-made shirts are able to propose a dozen collars, each one having a special use. Note that any type of collar is possible, but not for all occasions. For a shirt to be worn at work, prefer collars with fairly tight points (classic collar, Italian collar, English collar). For ceremonies such as formal receptions or official events (work, awards), collars are specially designed. For the rest of the time (meetings, parties), the open Italian collars and officers are mainly used, the first are classic, but give a relatively relaxed air, as for the second, they are a particular sign of originality, and literally break the very dressed side of the shirt, ideal for the evenings