Dont know where to shop

Hi, i am new to this subreddit and sustainable fashion. I am trying to get better spending habits in general, but i have a problem with clothes shopping in particular: My only seeminly sensible option is not ethical.

I live in a small country. Most of the accesible shops are fast fashion brands, mostly international. There are a couple of local fast fashion brands, which i am also avoiding and boycotting for various reasons. There are not many small businesses eighter, and existing small bussinesses i currently cannot afford. Also no second hand shops in my town. So i have to do most of my shopping online. But i cannot buy online from international brands because of taxes almost double the price.

There is a second hand shopping app, that has almost %90 of the second hand circulation. I oftentimes buy from that app, but i dont think it is completely ethical. First; the app cuts almost %35 comission (including shipping) in total. I think thats way too much. But my main issue is that the app is linked to a huge fast fashion brand. I guess it is better to shop second hand with a %30 benefit to fast fashion, then shopping directly from fast fashion. But i am not comfortable with it. I know this problem probably has no solution, but i still want to hear your ideas and suggestions. Thanks in advance.