As one experienced in such things, I will agree with saying "summon what you want," but I might add "go ahead and attempt to summon what you want."
Advocating study, caution, and the like has nothing to do with lacking skill or knowledge or being fearful. It is more a matter of respect and understanding.
To be frank, most people who attempt to do such things accomplish absolutely nothing and simply let their imaginations go wild. Usually they go on about their power, and skill, and the various marvelous experiences they've had. That, or they are new and just running their mouths - much like this sapphire individual who says specifically how new she is within her profile.
Paths that deal a lot in the evocation of higher spirits generally require a great deal of study. The Golden Dawn, Voodoo and Hoodoo, advanced initiates of Wicca, etc. all work with such things, but initiates spend years studying, learning basic ritual and prayer, and so forth before ever attempting these things.
If you would like to begin such studies, I recommend beginning with learning the rudiments of one of these paths.