different spells work better for different people. you might use an amazing love spell that uses saffron however, you don't have a strong connection with the herb so the spell isn't as strong as if you used one with dill or vanilla. same goes with how much energy you charge, when you make the potion and many other little things.
second, be sure you know what kind of potion you're looking for. not all of them are made in a bubbling cauldron, placed in a bottle and consumed. simply put, a potion is a liquid spell, you could have a tea, a bath, a lotion, or an oil for a few examples. this potion might also need to be worn, or be anointed like a perfume, it all depends what you're looking for.
but i'm guessing you want a strait up answer lol, while i've never cast it, you'll probably be referred to Love Potion number 9 the most. it's most likely posted on the site, if not, i have a copy i'll post on the forum [no one mail me please] this one isn't meant to be consumed though. [since it contains things that shouldn't be]