Personally I think the best approach to sustainable clothing is to buy second hand/used items; why waste resources making things new when we have so many wonderful things that already exist. Thrift stores are one way of doing this, however they are usually packed to the brim with items and can be pretty overwhelming. Recently I came up with a more methodical approach to thrifting to try and find a way to keep myself focused on what I actually want and will wear. I adore clothing and enjoy experimenting with it, which is why I've found this approach that I devote a lot of time and energy to, but you can easily only take elements of this if that’s not you.
I started by writing down every article of clothing I own, not including socks and underwear, to see the types of items I have. This gives me a clearer indication of my style and in turn the kinds of items I will genuinely love and use. Then out of that I made a list for things that needed repairs and adjusting, and a list for things I'm thinking of getting rid of. Once this base was all organised I got to the part which has made shopping sustainably for my closet a whole lot easier.
I started by writing out my colour scheme, split up into two sections: neutral colours and statement colours. Neutral colours are ones that I wear more on the day-to-day that suit my tone and can easily be paired with one another. For me this is black, white, and dusty green. These are more versatile items that can work for a range of occasions. Statement colours on the other hand are ones that I love and feel happy in but that are less versatile than my neutrals and that I will own less of. For me this is pink, red, orange, and yellow. You don't need to have 'neutral' colours in the neutral section, you can have neon green if it fits the criteria, it's simply a guide to help you understand your style and know what colours to look out for in the sea of clothes at the thrift store. For example, though I own a few blue items, I don't really like wearing the colour and don't frequently pick it out of my closet, which I may take into account if I find something blue in the thrift store.
I keep this all on a note on my phone, and at the top of the note I have a section entitled 'to thrift' which lists all the items I am currently looking for. Once again this helps me keep focused and avoids the piling up of loads of clothes. This list may be based on items I need (for example my last pair of denim jeans broke to an irreparable state) or items I want. My current note is below! I also use pinterest for inspiration, hope this helps make thrifting a bit easier and sustainable fashion more approachable!