Petra,
The first three words of your title are what Google pays the most attention to:
*weekend ladies tunic <- This one looks great!
*Empire line sky
*upcycled boyfriend shirt <- This one looks great!
*ladies denim cropped
*One-of-a-kind recycled ladies (a space, not a dash, separates words)
*recycled ladies denim
*tailored ladies denim
You need to ask yourself, if you wanted to buy that particular shirt, what would you search for? The best answer would become your title - and should be repeated in your description and your tags.
This same question is what you need to ask yourself when setting tags. Would YOU search for "tailored" to find a $130 jacket? or would you search for "tailored denim jacket"? If you wanted a casual weekend tunic, would you do a search for "weekend"?
After wracking your brain for hours, and then finally giving up on the whole SEO BS, if you have unused tags left, fill them with the one-word stuff and the "almost descriptive" tags like "eco friendly". Need one more tag? Put in your location - some people search for local sellers.
You have my congratulations on opening your shop, and my sympathy for the enormity of this project you've started. Don't give up - it can all be worth it in the end.