I'd suggest starting with 18% (18mg/ml, it's sometimes marked) of nicotine for a long term heavy smoker. That's where I started for the first week. I found myself hitting it very hard at first, both to satisfy the cravings and because I needed to keep my hand busy. When you get that dull headache above the eyes, that's too much nicotine, cut back to 12%. (I'm down to 6% now.) You can buy an off brand eGo type battery plus disposable cartomizer or two, plus a charger cord, plus a small case for less than $20 at most vape shops and all day online. Unless you're flat broke, I don't recommend it. You can't vape while charging an eGo type battery, so you'll have to buy 2 to keep you going. If you like that style, fine-- many people do-- but get one eGo branded and variable voltage, they call it the "eGo Twist." It costs a bit more, but lasts longer, and you'll still need 2. The 750mAh batteries are small and lightweight. The 1100 mAh models same length but larger in diameter and heavier. The big ones last longer before needing a charge. If you like disposable cartomizers, you can buy them in bulk online as low as 50 cents each; the vape shop will charge you $2-5 each. A carto will last for a day to a week and a half, depending on how hard you use it and how sweet your juice is, before it tastes burnt and needs to be tossed.
A step up from there, into the $40-60 range for a good battery and a replaceable coil tank, would be an Innokin VV 3.0V battery. It variable voltage or wattage, so you can control the power you're using, charges using a mini-USB cord, and is vape-while-charge so you can get by with one battery. Many people find the vape they're looking for in that power range; others move up and then go back. Online usually <$30. A step up again would be an Eleaf iStick variable wattage battery or an Innokin MVP. They come in different models, so price varies from 30ish to 60 bucks or so. Get the biggest the budget will stretch and you can use it, at least as a backup, as long as the battery lasts.
As for tanks, to get rid of the disposable toppers, it depends on the size. For small diameter, 2ml capacity, to preserve the vape pen look and reduce size/weight as much as you can, try the Kanger mini pro tank, the Innokin iClear 16 or an Aspire Nautilus mini. Larger diameter tanks, with 4-6 ml capacity, the Kanger pro tank or aero tank (I have several, very free drawing), the Innokin iClear 30, or the Aspire Nautilus. The Kanger Mini Sub tank, or the larger Sub tank, are well thought of, but you're not going to have enough battery to fire it well unless you get above a 30 watt regulated battery. All of these have replacable coil heads. When they start to taste burned, you replace just the coil, not the whole thing like a disposable.
Welcome to the board, and good luck getting off the coffin nails. You'll find a lot of help here; just ask.
