By definition "Casual" decks have a vague direction, which makes it harder for me to give advise on. I understand how it is to build with what you have. Enter in a "Maybe" board of potential cards that you have access to. I can also help with advise for the format, theme, build, and buy list if you want. I personally wanted to make a Pauper deck (all commons) based around
Akroan Crusader here soon. Your deck is 3 cards away from being Standard format in case you wanted to go that route.