magick is energy found in nature, as such it works within the limitations of nature. if a human cannot fly, then magick cannot change this fact. since magick is a force/energy, it can effect energy to bring things to you, a specific person, or group. spells for luck, love, wealth, and similar for instance can be cast because you are dealing with energy/forces, not physical changes or manifestations. the wealth spell, for example, you cast one for more money, this spell could work in a few ways, it could help influence your boss for a raise, or find money on the street or in the couch.
magick isn't black and white, so before casting you should think long and hard. as with the example above, the money found on the street has to come from somewhere, so it could of fallen out of someones pocket. personally, if this is the case, i chalk it up to bad karma on the person who lost the money, but if you find, say, 500$, i would put up some flyers before instantly spending the cash.
things that go against nature such as flying, invisibility, levitation and so forth will not work because magick cannot do physical changes, it's natural energy. just keep asking yourself 'is this in human nature' and you should be able to figure things out.
then you have grey areas, there are some spells that deal with energy, and in theory would work, but are so powerful and fate altering, many feel it cannot be done because humans should not [and cannot] possess that much power. these are weather and death spells. personally i would steer clear of both for at least your year and a day, then through your studies, you should determine for yourself if they can be done or not. keep in mind if these spells do work, you can receive a lot of bad karma or ill effects by casting. a weather spell doesn't part the clouds in your area, it would move an entire weather pattern so you receive sun. this rain though would have to go somewhere, and that place might not be ready for rain, resulting in a flood. similar with a death curse, you'll send enough negative energy onto a person to kill them, be ready for some major backlash, such as you getting sick, if you're married you could suffer a divorce, even the death of a loved one could come from such a terrible curse. so don't cast these spells lightly if you conclude they are plausible.