EgyAnar, whether a spell will work or not depends on a number of things. First of all, no spell will work 100% of the time and some won't ever work at all.
But the most important factor in whether a spell will work is the spellcaster themselves. Do they understand magic and why it works? How long have they been practicing? Are they feeling ill, angry, depressed, tired, distracted, etc? Your physical well-being can and does effect your spellwork. Is their focus and intent clear and direct? Do they fully understand how to gather and direct energy to a goal and is the visualization of that goal clear in their minds? Any and all of these things can have either a positive or a negative impact on your spell casting.
And then there is the fact that sometimes the Universe or the Gods or whatever counteract your workings. Or there is the situation, such as desiring snow in Egypt where the natural forces of where you live would negate any such working.
So it isn't a matter of which spells work most of the time. Whether a spell works at all isn't in the words or ingredients of the spell but in the spellcaster themself.