I Have Been Smoking For Ciggerettes And Weed For 16

I have been smoking for ciggerettes and weed for 16 years now am I am really determined to stop, today I am trying to cut one of them out but can not cut both out at the same time but I really would like to so I have decided to cut the weed out firstly from today and just smoke ciggerettes after a few weeks of cutting the weed out I can then focus on cutting down on ciggerettes then slowly cutting it out I know this is going to be really hard but I really don't want to be a smoker no more I'm 30 years only and have noticed my gums are going a dark colour and my teeth are getting gaps in them and was not like that before please can you help me and what do you advise ?