At 2 1/2 or 3 packs a day you'll be heading for a mod soon but you'll need an essential part of that - a 510 atty.
Kent C is right. You'll probably end up with a high powered mod in the end.
At 2 1/2 to 3 packs a day, your body is used to a constant, heavy stream of nicotine throughout the day. That's not an easy thing to overcome.
I was at about 1 1/2 packs a day, and I was able to quit with a 510 and 24 mg juice..... For about two months. I did really good until I had problems with my ex wife and daughter.
My wife on the other hand smoked about 3 packs a day, and she has had a heck of a time with it. She wants to quit, she knows she needs to quit, but the 510 just isn't enough for her.
I built a 5 volt mod for her, and she is doing much better with it. She is down to about a pack a day now. That is something that no one could have seen coming.
I would recommend starting with the 510. You can get a kit from
cignot.com for $35. According to the cignot website, they are currently out of the 510 starter kits, but expect more within the week. There are a lot of suppliers who sell 510 kits for around $40 to $45.
If the 510 doesn't work for you, take a look at the 5 or 6 volt mods, or look in the modders section at these forums. If you are good with a soldering iron, you can easily make your own 5 or 6 volt for a few bucks.