Hi Adamroy! Welcome, welcome!
I don't have as much knowledge to share as the others, but wanted you to know that I started vaping a couple of months ago on a Joye 510 (almost as small as a regular cigarette) and found that it was not as convenient as having a bigger battery that could get through most of the day. I just switched to an eGo (have 900 and 1100 mAh batteries) a couple of weeks back and really like it. Like dormouse (awesomely helpful response!) was saying, the 510 connection is pretty easy to try new things out with, there is a lot to try out there with this connection and lots of it can be used across models that share this (but be careful to use the correct charger, those are often different for each model, even if the same connection fits. If you choose a smaller style, just don't buy too many extras in case you soon want something larger. I bought too much, thinking I would never be comfortable with a big battery, but now I guess I feel kind of lucky that I have emergency back-up. It really isn't wasted money. Sometimes you may prefer to carry a smaller PV in certain places, so for me, having both is nice. Lots of people here joke about the reactions they get when they pull their "pipe bomb" out in public. Just buy a modest kit that appeals to you now and get started! I'm so happy you're here.
Good luck and good health!