If something is bank, it's dope, cool, etc. Thus, "The Bankest" would be the most successful version of all of these terms because it has the "est" at the end.
A promoter or follower of what is related to banks, banking and money.
John is a bankista, he knows everything about banks.
Sara is such a bankista! She definitely enjoys her money.
I like to read that bankista magazine and get informed about banking news.