one does not 'master' it, magick is alive, there are new components you will discover as you continue on your journey. while no one is perfect at every type of magick, start slow and keep trying.
all magick is energy, if you can feel the energy, if you can work with it, you can cast any working spell. granted, there are many reasons why a working spell would fail; inexperience, lack of energy, lack of focus, or a lack of need [casting a spell to show off for example] can cause a working spell to fail. while a large component of magick involves the caster, the universe/deities do have a say in the matter. if you cast a money spell when you already have more than enough, the spell won't work. constantly recasting because 'this spell doesn't work' and not learning from the universe/gods can result in a more severe lesson. [say someone steals your identity and takes all your money] you need to be observant since magick isn't straight forward, instant, or what you expect.
if you're having trouble finding a place to start, and you've already gotten the basics down, try meditating on the question, or reading an article about the various types of magick, get a feel for the style, then try a spell to see if you work well with it. keep in mind you should only cast spells that are necessary, not for practice or selfish reasons. good luck, blessed be.