Just because you don't like shopping doesn't mean you shouldn't try to look good. Here is Young Post's list of wardrobe essentials that every man-about-town should own - anything else you add is up to you.
A nice shirt won't hurt
While you're forced to wear a school uniform, you might hate the idea of wearing a smart shirt if you don't have to, but a long-sleeved "button-down" is really useful for family events, interviews, or a date.
Get a non-iron or easy-iron one in a pale blue, purple or pink (yes, pink!), and pair with jeans or khakis when you need to dress up. It also works well under a jumper when the temperature drops.
Man up and layer up
When you've got to be smart and warm, save the hoodie for time with your boys, and throw on a round-necked jumper. Choose a neutral tone - black, navy, grey, even maroon - so you can wear it with everything. Pair with a T-shirt (make sure the neck of the tee doesn't show above the neck of the jumper) or button-down and/or jacket, depending how cold it is, and you'll be warm AND smart enough to hang out with Granny and her mahjong pals.
Be a style trail-blazer
Even if you don't have to wear a suit, it's not a bad idea to have a blazer in your wardrobe. No, not the one with the school badge on the pocket, but a less stiff, cotton or jersey version that you can wear to dress up jeans, or as another layer before it's cold enough to need a coat.
You've got fashion in your jeans
Jeans are the most versatile item a guy can own. You can wear the right pair almost anywhere (except school/your cousin's wedding/that interview for a summer job). Choose a dark wash, and a straight-leg cut - anything too skinny or baggy looks too trendy, and is often impractical and uncomfortable.
The fabric should be close to your skin, but not tight. When you try them on, make sure you can sit comfortably. And make sure they are the right length: the back of the leg should come at least to the top of the sole of your shoe. Make sure you're neither showing your socks nor dragging the cuffs on the ground.
The facts about slacks
When it's too warm for jeans, but shorts aren't formal enough, you need another option, and that's where chinos or khakis come in. These cotton trousers can look super casual, but are smart enough for a family dinner, especially if you iron a crease down the middle.
You don't actually need to buy them in the colour "khaki" - beige or light grey works with more colours.
Take stock of your socks
The only time you should wear white socks is when you're playing sport (or if they're part of a uniform). If you're dressed formally, you MUST wear dark socks to avoid looking foolish - black, grey or navy are your only sensible options.
For casual wear, you can show more personality with patterns or cartoon characters.
Don't beware proper footwear
When you're not wearing school shoes or trainers, and Converse just aren't smart/practical enough, go for either leather desert boots or "bucks": something with a rounded toe, and three, four or five holes for laces. They're smart, yet not so fancy that people will assume you're heading to a ballroom dancing competition.
Super sneakers
Converse are pretty timeless, and work with everything from shorts and T, to date night. Choose block colours rather than patterns: black, white, red or grey are all good choices. And go for the low-top rather than high-tops. However, the cloth inside can hold on to sweaty-foot smell, so try not to wear them day after day.
It's a good idea to sprinkle some bicarbonate of soda inside and leave it overnight, then shake it out before wearing.
And from the expert (ie a guy):
Unless you're playing sports and need support - in which case wear jockeys / briefs, or even boxer briefs - boxers are the way to go. They offer maximum hygiene while being minimally constrictive. Always go for 100 per cent cotton as other fabrics can get too sweaty. Avoid waistbands with exposed elastic as it can irritate any hair follicles, and watch out for annoying tags on the inside of the waistband. Rip them off if you can, or just wear your undies inside-out.