I too am fairly new but here is my experience...
1. Go with the eGo or Riva...I think the battery life on some of the smaller cig like look or "pen-style" e-cigs would drive me crazy and make me feel like I have a part time job. Usually one Riva 510 Battery lasts me all day and I don't have to worry about switching them out or carrying a charger. The vapor is nice and the TH is really good on 24mg nic juice.
However, I am pretty comfortable with having a device that has a manual button (Please reference the links from Numevexo as that information really is unbelievably helpful) and doesn't necessarily have the same exact feel as a cig. It really isn't much bigger, but for some folks it may seem very foreign. I for one was just not hell-bent on replicating the sensation of smoking a cigarette and rather wanted a nic and "smoking" habit substitute.
2. Juice, juice is the key..until you find a juice that you like it will be more difficult to really enjoy substituting vaping for smoking. My advise is to order multiple juices (likely different flavors, nic levels and from different vendors) to just find out what you are going to enjoy. I really thought I'd like tobacco flavors, but after trying my first one I was very quickly drawn toward the other flavors as I enjoyed them more than my regular cigs. Allow yourself to try different things and you'll find something you'll like.
3. Do your research...
on youtube I found Doctor Vapor and MistressNomad's videos to be REALLY helpful.. and occasionally Moobyghost and ShanB's videos were great too..
YouTube - DoctorVapor's Channel
YouTube - MissNomad89's Channel
and
YouTube - moobyghost's Channel
YouTube - ShanBurkholder's Channel
And I can't stress enough how helpful it is to follow Numevexo's advice and read those library and first timer threads.
4. A couple of suppliers I really have had great newbie experiences with are..
www.liberty-flights.com
www.freedomsmokeusa.com
Can't say enough about how positive my experience has been with both of those companies!
Good luck and happy vaping!