To understand if a supplement is right for you, you'll have to ask a doctor and maybe do a bit of homework. The best way to figure it out, is to understand how the supplement actually works inside your body. When you know what is happening, everything else becomes much easier.
An essential nutrient is one that you must have in your body in order to survive, as your body needs it to function. The Mayo Clinic defines L-arginine as a semi-essential amino acid, which means if you're not producing adequate amounts, you'll need to eat unreasonable amounts of food or you'll want to take supplements. You won't die with an L-arginine deficiency, but you will suffer from some uncomfortable symptoms; you'll feel weak.
L-arginine makes urea, the byproduct created when your body breaks down fats and proteins. The amino acid helps regulate waste, which in turn will regulate nitrogen and other chemical levels in your body.
L-Arginine also makes creatine, a protein, which helps promote muscle growth and strength. It also helps the body get rid of the waste from said protein.
As a supplement, L-arginine expands the blood vessels, which allow more blood through. This is how it lowers blood pressure, and subsequently, the risk of heart failure. It's also why L-arginine is a great treatment for erectile dysfunction.