The most sustainable thing you can do is keep, care for and repair the clothing you currently have. The next best is to create a capsule wardrobe from local, second hand clothing (the most sustainable way to shop). A capsule wardrobe is made up of essentials, ideally a mix of ethical basics and well-made vintage classics - that way the style endures [unlike trendy looks].
This is not about cookie-cutter minimalism, in fact, no two capsules should look the same. Your wardrobe should be a reflection of your life and personal style, your work, hobbies and the climate in which you live. An accountant by day, artist by night will have a much different wardrobe than a farmer who surfs on the weekends. Your capsule may have more items than someone else's. As long as you enjoy and wear everything in there, it doesn't matter if you're not a minimalist at heart. It's just about increasing the amount of times each garment can be worn and used, to get the most out of the resources that were already put into it.
At this time, the global textile industry has a very negative impact on the earth and the people who are employed by it. We need to reduce the amount we buy and the amount we waste, and stop treating garments as disposable. We also need to make sure those working in this industry, and our planet, are taken care of. The answer is to buy less, and use what we already have. Reduce, reuse, recycle should sound familiar, it's the golden triangle of sustainability after all. The clothing we currently treat as garbage is actually a gold mine of opportunity. We need to treat it as such.
02/ Saving Time & Money
Your closet will be organized and easy to navigate because most things will match, and every item looks good. Less time looking for items amidst a pile, trying things on and clothes not fitting. Once you have a plan for your capsule, you can look gradually to buy your perfect vintage pieces. You're saving money short term by buying second hand, and avoiding insane retail markups. There aren't too many items I can think of that are necessary to be brand-new, whether clothing, furniture or beyond. You'd be surprised what that in-store experience and those marketing campaigns cost. In the Grey Market, those margins no longer exist. Long term, you save by keeping quality pieces around for years, or even generations. The more you can wear an item, you are reducing your cost per wear.
[cost of an item divided by the number of times worn = cost per wear]
03/ Better Style
Your closet will have only pieces you love to wear, a multitude of different outfit possibilities and a look for any occasion. Enough said.
You have to go through your closet and lay out every piece of clothing you own. You could try watching Marie Kondo on Netflix - she has inspired many to clean out their homes and to keep only items that spark joy. Or you could try sparking a joint. You may want to invite an honest friend to assist. Either way, you will thank yourself later.
You need to find out what you actually wear and the functionality, style and colour of those items. The key is to organize into functional groups, look at the predominant colours and styles, and go from there. Don't forget about footwear and accessories. What you're looking for here is to match your items together within each group, creating as many outfits as possible.
Daily - socks, underwear, t-shirts, jeans...
Work - uniform, suits, performance wear...
Hobby - sporting gear, athletic apparel...
Social - formal, suits & dresses....
Seasonal - winter coats, bathing suits...
So, all your workout gear can be neon pink because you won't be trying to wear it with your work suits or formal wear. But your work suits and shirts should match each other and be inter-changeable to create as many work outfits as possible. You want to be able to wear each item a lot, reducing your cost per wear.
The best thing you can do for the environment is to care for and repair the clothing you already own. Keep items that may not be of high quality if you can/will still get wear out of them! The idea is not to throw out everything and start again, it is to build on what you have already, have pieces that are versatile and to make better buying decisions going forward.
Items that are damaged or ill-fitting can be repaired and tailored, usually only financially worth it if they are of a substantial quality (another good reason to buy better in the first place). Learn to do some basic sewing or find a lovely neighbourhood tailor to help you out with more complicated endeavours. If your clothes fit you well, you will look good - period.
You're aiming to have as many matches within your clothing groups to make as many different outfits as possible. This may mean neutral colours for some, which can help create more matches. But there is no reason to shy away from patterns or colour if you're comfortable wearing them. If you see or already own a great but unusual gem, just think about 3 possible outfits you can make with it [out of items you already own] and let that be your guide.
You should be honest about what you don't wear. Note the amount of waste and the cost of the items, it will be a reminder to prevent impulse purchases in the future. Realize how many resources were used to create that piece of clothing. At the same time, don't be too hard on yourself - we're all trying to do better.
If the item is high quality but not for you, it may have redeemable value on the grey market. If it’s a designer label, you can contact a consignment store, or try online consigning through a reputable dealer [look for resellers that authenticate luxury goods or pay for an authentication service if that's what you have to sell or want to buy].
If it's mid level or fast fashion, you can try selling it yourself via an online marketplace, but I would recommend a local consignment store if you need to make some cash without too much trouble.
If you can donate it, a thrift store or charity shop will use the profit for good. These are either small businesses or not-for-profit organizations, often providing the best deals in the entire second-hand market. Only donate clean and orderly clothing to thrift stores - they will appreciate you even more! The better the clothing you give, the more they can do for the community.
The last option is the larger, for-profit franchise [Value Village/Savers for example], however these options are better than the landfill because may they have the resources to deal with low-grade/trashed textile items, such as downgrading into industrial rags/stuffing. Please know that only some stores will recycle damaged or unusable items, many just throw textiles out if they cannot sell them (chains and independents). Make sure you ask about their policies and ensure that there is a recycling component.
Now you should have an organized closet full of pieces you love and are excited to wear! Pieces that have been fixed and fitted will be like new. Try different combinations and looks - most of your clothes should be working together. You get to shop through your closet and rediscover what you loved about each item in the first place. Mix and match items that you haven't paired together before. Accessories are a great way to freshen up a look.
As you wear more of your closet, the gaps and missing links will become obvious. Are you too casual at work functions, maybe you're missing weather appropriate outerwear or a pair of shoes that would dress up some casual items? You will learn a lot about your personal style and what details matter. Keep a list in your phone so that when you come across a great buying opportunity, you'll be able to keep your eye on the prize.
When you take the time to find special items, you'll learn to love caring for them and treating them kindly. This makes them last longer and look better. If items fall beyond repair, they can be replaced with better versions going forward. Or there's always the opportunity to have lightning strike twice in the world of secondhand, and find that dream item once again.
Now that you know what you're looking for, you have to go find it. I've personally been stalking the world's most perfect resale motorcycle jacket, which is illusive and rare in the wild. However, the more that people are donating and reselling, the more gems there are lurking out there in the most unexpected places! The key is to purchase items which you know work with the rest, have great quality and that you'll actually wear. Don't let the price or novelty of second-hand items trick you into buying - stick to the list.
When it comes to newly created items like socks and t-shirts, the ethics can be confusing. Ideally you're looking for natural or upcycled fabrics that are considerate of the environment, and garments made by people who are being paid well and treated fairly. It's important to look for quality here as well - the longer the item lasts, the better (less resources used, less waste and less time & cash spent).