Im not sure there is a length of time it takes per say. It's all in ur comfort level. I found a great site that you may want to check out. I love it and the lady the created it. Biddytarot.com. brightest blessings
If by master you mean how long it takes to get to know your deck, then I would say it takes years of practice & one heck of a memory. You'll see how the cards relate to your life as you go, just try to apply what you learn from them to yourself & situation. Everyday life isn't always something we need divination on!