Using pre-written spells is a bad idea is because the karma of the person who wrote the spell affects you when you use it. I collect spells to help get new ideas when I'm in a spell-writing mood, but don't need a spell at that particular moment, & I also use spells to see what sort of objects {stones, scents, etc} that people use for specific purposes. If you're not inspired enough to create your own spell, or too lazy to, whatever the reason, maybe you better re-think Magik as something you want to do.
Just thought I'd warn you. Now on to the spells