If you want to bring up the gravity plain corn sugar is fine. Don't put to much corn sugar in because it will cause an warm alcoholic flavoring. But for some DME I would suggest having some light or amber, can use them in almost every recipes, even porters and stouts.
Primary Dusseldorf Alt
Secondary Russian Imperial Stout
Bottle Conditioning Janet Brown, Russian Imperial Stout.
On Deck Ryed Up Kolsch