18% chance means every time you click you roughly have 1 chance to succeed and 4 chances to fail. And there is no "memory" in the system, each click is unique. You can click 1000 times and fail every time, you can click once and succeed. That's a general point, and I am just making it because most people don't understand probability. There is no mathematical reason for you to definitely succeed if you try 5-10 or 20 times just because it says 18% chance. If you look at it rationally, the odds are stacked heavily against you.
Now, the bright side is people have wasted hundreds of Gem Energies trying to upgrade jewels, that's why they are so expensive in the market, you just wasted ether. But as a general rule of thumb, gem energies are he better way to go. To get those 20 lvl 3 rubies, you definitely "lost" many lvl1 and lvl 2s