Graphene by definition is a 1 (not two, three, or multilayer) atom thick carbon molecule. The single layer 2D lattice of carbon makes the unique characteristics of graphene possible. Graphene is a single layer of Graphite. Multi-layer graphene is a contradiction in terms, it is graphite not graphene. There are numerous companies claiming to be graphene manufacturers and selling graphene at very attractive prices. But if you look closer they are advertising graphite (multi-layer graphene) not graphene.

Once you are certain that what you want is graphene not graphite then you should look at quality.  Quality determination relies on proportion of mono-layer graphene, level of impurities, flake size (if flake), ratio of carbon to oxygen, and other criteria based on proposed application.