In my mind/experience, an RDA is an RDA. There's really not much to em. Few things to look for:
- Deck/chamber space. The more of this there is, the easier it is to build on. But also consider that larger chambers require bigger, more high-powered builds. Something in the middle will give you the most range while still being easy to build on.
- Post layout. Avoid the exotic ones for now. The two you should look for are velocity-style and split-center-post. The velocity-style has two posts - one on each end with two holes stacked on top of each other in each post. Split-center-post is similar to the velocity-style, only with a t-shaped post in the middle. The outer posts have one hole, while the middle post has two holes side by side.
- Airflow. Don't just consider size, but adjustability as well. Consider single-coil and dual-coil compatibility. Some do one or the other, while others do both. Get one that does both. Starting off, the more airflow options you have, the better. Later on, you can pick more limiting ones once you know what your needs are.
- Build quality. Obvious implications here. Reviews, comments, and pictures will reveal obvious flaws.
- Price. Great RDA's often come at a higher price, but some of the best RDA's are cheap. I think you should try a handful of cheap ones first and then start looking at a $50+ endgame, if you want. Or maybe your endgame will be a cheap RDA... ...you never know. My favorite to date is the Mutation X v3, which when it came out was in the $20-$30 range. And then, there is the Snubnose, my second favorite, which ran me about $70. Point is, many of the cheap, "newbie-friendly" RDA's are the very same ones that veteran builders reach for first.
The actual building process is simple. Watch some youtube tutorials to see the general process. The harder part is finding builds you like. It will take a lot of trial and error. We can give you advice on what builds to do all day, but until you've figured out what builds you like, it's not going to be all that helpful.
Steam Engine is going to become your best friend. It helps you figure out how many wraps to do with x wire over y mandrel to get z resistance.
The coil master kit has everything you need. The price is right, too. Go for it.
For wire, I recommend that you get an assortment of kanthal and just play around. The classic gauge spread is 28-26-24. This gives you good range of builds to experiment with right away. If you also want to do TC, stainless steel is probably the best choice. You can actually use it in power mode and TC mode. So feel free to go for SS instead of kanthal if that's the way you want to go. Unlike nickel, it can be dry fired for cleaning. It saves you a lot of money over keeping stocks of nickel and kanthal for experimenting with VW and TC simultaneously.
Another thing to consider in the long-term is cotton. Our prized organic, unbleached Japanese cotton can get expensive to buy domestically. But quality cotton is important. I recommend you hop on amazon and buy a ton of it for cheap direct from Japan. My vote goes for
Muji. That's at least a year's worth of cotton, though it takes a while to get to you.