Therefore if you truly desire to stop, you will do this naturally :>)
What I would suggest is that you decide what you would like to do instead of smoking? What new desires you would like to explore and dream about, to spend all the money on that you save from naturally wanting to improve your health?
You will also substitute an activity that is destructive to your body for a constructive one, by moving away from poisoning your body through the inhalation of poisonous gases.
This is a very personal thing and only you know what brings you greatest happiness and joy. My own advice if I were to offer some would be to look within your Self, find your own inner dream which you have always wanted to do, and go and do it.
Regarding avoiding weight gain: if you create a vision of your perfect weight in your mind