Welcome Simon!
There are probably a number of questions I should ask first, but.....
If I had to take this path all over again, I would go for an iTaste (or iTazte) VV3. It's 510/eGo threaded, so a number of different toppers work well on it. It's got variable voltage/variable wattage capabilities. It is only an 800 maH battery, but can charge while you're vaping (unlike many of the eGo/Spinner-type batteries. It's relatively inexpensive (about $30, shipped from
Driving down the cost of vaping! - 101 Vape) You would need a topper of some sort. I like my EVODs and mini ProTank 2 (this one is glass, less likely to be damaged by "tank-cracker" juices)
There's a "big brother" to the VV3 called the MVP2 (I have both the MVP and the VV3, as well as Vision Spinners and some smaller eGo-type devices.) It's a "box" form (slightly smaller than a pack of cigarettes) with a 2600 maH battery (i.e. can be used longer between charges)
You're going to get a whole swarm of responses. Look at whatever folks are recommending. You need to think about how and where you're going to be using your gear. How much "effort" you want to put into upkeep/maintenance, etc. You can go CRAZY with tanks and mods and flavors and whatnots. You can get into rebuilding and making your own juice. You can chase clouds....
You can also keep it simple - merely a reliable device (WITH A BACKUP) and some decent juices to keep you away from smoking (presuming this is your motivation).
You don't have to spend $100's or $1000's of dollars. Do you homework - check out what others offer on here as far as their recommendations. Remember this is for *YOU*. What I have may not be the right answer for *YOU*. But, if you research a little up-front, you'll likely spend less in the long run.
Good luck - keep asking questions....