In my opinion, 15 years old is too young for starting experimenting with psychedelics... I did have my first shroom trip at 16, but now that I'm looking back I was too young. I didn't have the maturity for it before I was something like 17 and a half. Although you might think you are mature enough and stable mentally, I assure you you are not. I think it would be better for you to wait at least 2 years before having your first psychedelic experience... But I know there are low chances that you will listen to this advice, so if you decide to do it anyway, please at least follow the advices people gave you here. And maybe taking a lower dose would be a good idea.
But the best advice is to wait. You are still growing up, so is your brain. Taking psychedelics while your brain is still developping might result in it developping in a... funny way...