I'm trying to develop a Dragon deck for my little nephew for casual play that centers around Horus The Black Flame Dragon and I was wondering if any one have any ideas.

Giant Trunade
Jinzo/Decree
maybe Lightning Vortex

Giant Trunade is useful for getting rid of any trap cards that might be on the field if Jinzo/decree is not on the field. Lightning vortex to get rid of monsters on your opponent's side so they won't have anything on the field to defend against Horus.

I've got a little question when it comes to Jinzo. Is it even worth trying to run an Amplifier in a deck that has Jinzo?:o

Sorry, i don't really know. It probably just depends on how many trap cards you have though.