Welcome to SoM! I recommend searching the basics, which help you learn to focus your energy into whatever you want, and using it. Your religion doesn't matter, it only depends on your will to learn and achieve what you're out for.
Practice makes perfect, really.
When casting a spell, you have to think about what your results should be. If it seems to be impossible, then it probably is. If you really can't work with other people's spells, try writing your own. Adding candles, crystals, herbs, etc. Can help with focus or strength.
Good luck, deary! :)