Hmm,in my opinion that should be electronics and gadgets because we can often see some deals online and also clothes I think is a big one.That should be the top selling products as far as I'm concerned.
Gadgets are sold a lot for bitcoins but I think that digital goods in the overall is way more sold than gadgets, at the other hand its more upcoming so that is nice and this means it has a good future.
Digital goods stay indeed on top because its easy to sell them for bitcoins and physical goods are just way harder to get at the first place and also sell and ship to a customer so its logical.