So yesterday i had my first salvia trip with some 10x extract. My friends and I had so much fun doing itthat were planning to get some 15x and kep going up. Anyways, is there much a difference in strenght between 10x and 15x ?

10x was light compared to 20x. I went from 5x to 10x, wasn't getting a good trip so I tried 20x and was blown away. I'd really like to get my hands on some 40x, pack a bong and see where it takes me. It's illegal in my state now.

10x does me in more than enough, I don't think I'd even want to smoke anything higher

Like marijuana, certain salvia plants turn out more potent than others. Because of this it is unwise to always trust the extract. I have had 10X before that was stronger than some 40X my friend had. If you do get a new potency, even if it is only 15X, I would recommend taking a small/medium size hit before you go crazy just to test how potent your salvia is. Welcome to the world of salvia, it is a beautiful place.