what do you need help with? what type of spell? the spell might now work because the type you're trying to cast isn't real. magick isn't like what you see in the movies, if you're casting a spell that goes against nature [like to fly or turn into a cat] it won't work.
another reason your spells keep failing might be because you don't know how to charge energy, focus, and visualize. items, moon phases, and skill all play a part in casting, but if you don't have energy and focus, you're not going to get far.