Instead of ignoring him, try helping him with his problems. It sounds like you are a good guy and he knows that. He might just be reaching out for someone.

It's hard to help people if they blow smoke in your face. (Literally)

Just move on... What's he doing to you? You don't have to be friends with everyone you meet. Turn him down enough times and he'll move on. The last thing you should do is lecture him on what he does, especially if he's just been trying to work up a common ground and make a new friend. You have no obligation and it is not your place to preach to some kid about his choices. Hang out with your friends, he'll hang with his. You're worrying too much about it

Well then obviously he does not want to be your friend. If your not throwing bible verses at him then he has no reason to do what he is doing.

I don't mean to sound quirky or anything but if he is asking you to buy cigarettes for him and his friend is peer pressuring you into doing something you don't want to do, you are letting them be in control. In other words they are the aggressor and they are making all the demands. You are at the mercy of saying 'yes' to give in and stay friends or you can say 'no' but you will feel bad doing that. That is their strategy of peer pressure, making you feel bad about saying 'no.'

What you need to do is go Renegade and become aggressive in speech saying that your foundation will not be shaken up. You are confident and loud in the way that you say no and you will stand up to your beliefs to the bitter end. In other words YOU are the one that needs to be seen as taking control of the situation instead of being at the mercy of it.