D3's most important combos come out of his down throw. There's so many options you can take on out of it, such as forward air, back air, and up air. You can even do a psuedo-chaingrab with up air, with doing a down throw, shorthopping, using up air than fastfalling before the last hit connects, and grabbing your opponent again once they get into your range and repeat. I've seen most people do this to rack damage up to around 50-60%, but I haven't tried it out myself oddly enough.
Gordos are an integral part to his play as well, and you can do crazy stuff with them. You can angle the way they're hit by tilting them after doing the side special, up, default and down. Default travels the most distance but probably the easiest for your opponent to intercept, up tilted gordo travels a very short distance and just bounces up and down, down tilted gordo (I think) goes 2/3rds the distance of a regular Gordo. I can't check SmashWiki rn so correct me if I'm wrong. I barely use down-tilted gordos tbh. Up Gordos I'll say is useful for those on the ledge since it covers their ledge getup options, and you can even use an up-titled gordo on somebody who's trying to recover from offstage, most of the time it stage spikes them.