this is something that i have been thinking about as a retailer as well-supporting lines that not only are made with sustainable/upcycled fabrics, but can be worn several different ways, limiting the amount of clothing you have to buy in general.
some of the items i have found:
Lirola: from Israel, has a dress that has 7 different looks, that is 7 dresses for the price of one...now we are getting somewhere!
(and this is without accessories)
Le Muse: loving this tiny line of knits that have a number of uses-off the shoulder, off both shoulders, blouse, dress or perfect for maternity...at under $80 you can go wrong.
Natural High Lifestyle: i LOVE this Santa Monica-based company that sells simple, sustainable clothing geared to the yoga/surf/nature loving person. Their bamboo sarong is always a big seller in the store-not only because it is the softest thing on earth- but you can wear it as a dress (shown 2 different ways below), as a skirt, a chunky scarf, a head wrap...this is must have for sure! which reminds me that i need to order these...
De Gala and Conscious Clothing: both businesses make sustainable lines, but they also make tube dresses that can have multiple looks.
The first, from Conscious Clothing can be a dress or a skirt. paired with different tops, leggings and accessories and you have a lot of outfits.
The second one, from De Gala is a basic narrow tube dress. but it is a super-simple foundation for just about anything.
i will post more as i find them.