In order to make your very own deck of cards you need to do lots of research. Why? Because in order to create your version of Tarot you need to understand why the symbols on those cards are there and what the Tarot is really about. This means you have to do lots of digging in the past about Tarot, symbols, arts and craft (What kind do you want? Like zombie tarot deck and ect?), the title, the story of the cards, and lots more.
I say, don't rush. Just take your time because if you rush this than you will never create your very own best tarot.