All kinds of spells work, within reason.
Fantasy spells are simply a no no, the rest is simply common sense. If it sounds too good to be true it probably is, so vampire, immortality, instant healing, etc are all complete fantasy.
Magick will not effect any aspect of your life if you are not willing to help yourself, money, friendship, love spells and others will do you no good unless you are willing to put yourself out there and earn it.
The one big thing is that most spells written by others won't do you much good, the best spells to use after you have mastered the basics are those you have written yourself, they are so much more personal.