I cant cast magic

Because it isn't possible to make magical fireballs Mike. -_-

That is exactly the reason why it is important to choose a spell that potentially works. ^^

The spells you choose to cast basically have a huge influence over the outcomes you're expecting to get by attempting using some advanced spell work, which means they should be designed specifically for your intents, desires, and the main motived you had for the need to cast spells.
Using good spells is metaphorically the same as using good tools and packages for your living. Which is exactly why you must have a good spells while getting to work with spells and casting.
So, what you need is to have a spell which chooses specifically your intents as it was designed for this reason. Secondly, the spell must me comfortable for your use and you should be able to feel connection with it, which means that it is the right spell for you to choose for your casting.
Finally, the spell must be logic, and magically possible to achieve. Which means, spells associated with fluff and fantasy are a huge waste of time, which is something you do not choose. The real magic spells though, who spiritually has the potential to work, are the spells you should work with and get the best of results, considering the fact it spiritually has a lot of potential to work.
Whenever you're trying to look for a spell, check these criterions by asking yourself: does this spell choose my intents, desires and motives? Do I personally like this spell ?(yes, you must feel good with yourself while casting the spell. It is important for you to like the spell as it's your "tool"). Is this spell accurate enough to achieve my goals?

Starting a snow storm, nor creating a fireball are fantasy, so will not work. You cannot go against nature. Keep in reality and stay out of fake stuff. Common sense will help here. You will succeed if you will do the correct learning. Read, study, learn. Blessed Be...

Mike, the fireball spells are fantasy spells. This is not a D&D game and magic doesn't work that way.

Well, a snowstorm spell won't make it snow in the desert, but if there was already the possibility of snow occurring I think you could have induced a storm. My family once did a similar thing with a rain ritual targeted at a specific location. There was already the fair chance of snow, we just wanted to make sure it did (the relatives that my crazy relatives call crazy would have visited if it hadn't, we really didn't want to see them).