Assistance with making a deck

I am in a tournament with my friends that we are doing special rules for, mainly a n/r rarity tournament. However after looking online, most of the n/r decks I have been shown seem to confusing for me. Can anyone give me some advice as to what would be a simple, less 12 chain combo to boss field deck?

as a side note as part of the rules we are allowed one card of any rarity to use as well