DOLCE & GABBANA BAGS

The RealReal is a community of about 40 million members, the largest platform for authenticated luxury resale in the United States. Founded in San Francisco, California in 2011.
The currently have 17 stores in: California, Connecticut, Florida, Illinois, New Jersey, New York and Texas.

This firm is based in Dubai, founded in 2012; and gives you access to a huge market of ultra luxury items from a very wealthy region of the world. For that region owning Dolce & Gabbana products and Dolce & Gabbana Bags is very common, some of the people there wear such items daily.
The Luxury Closet has a mix of items they stock in their store and are selling directly as well as items they are selling for regular people or items other commercial sellers list on their site.

Fashionphile is based in California and with stores across the USA.
They have perhaps the largest selection of in-house Dolce & Gabbana Bags in the world, their prices are for the most part very competitive.

Chairish was founded in 2013 and it is based in San Francisco, California, USA. It is the concept of a couple, she, a previous fashion marketing specialist and he, a tech (travel industry) executive. They have a focus on vintage and pre-owned home furnishings and home decor, but they offer pre-owned fashion accessories as well.

Rebag, was founded in New York City in 2014. They offer a mix of their own inventory and inventory on physical consignment (they physically take in the item to verify its authenticity and condition). They have boutiques in California, Florida, and New York. They have one of the largest selection of pre-owned Dolce & Gabbana bags.

Based in New York. They were originally an art auction house and now they are one of the important online sales venues of ultra luxury items.
They have great pictures and depending on the seller they will have enough information about the items, they provide an easy way to contact the seller and you can even make an offer directly on the listing.
As far as pricing, like many other sales venues, the price will reflect an increase due to the commission they charge to the seller. Still there is a constant number of good opportunities to find.