I have to say it's unlikely getting inked will reduce any future cravings; if you're feeling the need,you're feeling the need. Getting a tattoo can still be a very good idea-it's a great form of self-expression, and it can go you increased confidence if the work is good quality.
Obviously, getting ink with a druggy subject is a bad idea; do you want to be walking around with a trigger permanently marked on your arm? It's important you get something with a deep and personal meaning to you-it will be with you for the rest of your life, so you should spend a bit extra and go with a really talented artist.
I've only got one tattoo; it's a large self-devouring snake on my left hand-an ancient symbol for reincarnation, which is something that means a great deal to me. Rather than opting for black ink (it fades fairly quickly, and faded ink doesn't look good), I went for white ink instead. The effect is very subtle and pretty cool; it looks like scar tissue. When it does fade in time, it will be completely invisible, and that's fine with me, as I'll get another one in the same place. (Probably an Egyption Sacred Scarab-also a symbol of rebirth.
OP I wish you the best of luck getting off the gear.