One does not have to be fancy with spells. It don't matter if it rhymes. It doesn't matter how long it is. It doesn't matter the time it takes.
What matters is whats going on in your head once your doing the spell. What matters is the relations between you and the deity (If mentioning any). What matters is that you clear your mind, concentrate energy in your spell. Believe in your spell, live by your spell. Fell the emotions between you and your spell. Visualize and meditate on that spell. This is what really matters. Your spell can be three sentences long, just do what matters!