I recommend you read and study this page: It will give you a basic understanding of why volts, ohms, and watts matter and relate to each other.
Here is one on batteries:
You are correct. The first thing you need is a good ohm meter. It is mandatory.
Wire and wick: I bought a spool of 32ga 30ga, 28ga, and 26ga each A-1 Kanthal I get it from Temco. I really only use the 26 and the 28. Wicking i use organic cotton balls from the drug store, and rayon from Sally's beauty supply.
Then use these calculators to help you calculate your coils:
http://www.steam-engine.org/coil.asp
http://coiltoy.ermeso.com/
I would recommend a small precision screwdriver set. These are great for the screws on the RDA and also winding coils on. Small drill bits work great for winding coils too.
You might also consider a coil winding jig, and a micro torch. They just make things easier. Kanthal comes pre-annealed from the factory, but torching it makes it a bit easier to work with. The coil jig wastes a bit of wire, but it is very easy to make pretty coils.
Oops, I forgot you will need some small pliers, tweezers, and clippers to trim wires.
For batteries, I suggest the 18650 Sony VTC3, VTC4, or VTC5. Be very careful where you buy them, they are highly counterfeited.
Here are 2 very trusted sites:
http://www.vaportalk.com/product-category/ecig-batteries/ecig-mod-batteries/
http://www.fadoravapor.com/store/index.php?main_page=index&cPath=16_54
There are many other batteries out there. Many of them will work fine, but when you are first starting out I would recommend sticking with name brand, and trusted suppliers. Don't forget a good charger. I like the Nitecore brand.
I don't have enough experience to help you much in the area. I only have 2 types. I use the Tobh clone, and the 454 Big Block clone, both work great. They both are not the best for beginners. The Tobh has to be modified, or build off center for airflow. The 454 uses a ring for grounding and can be hard to build on.
I recommend YouTube and watching RipTrippers and Pbusardo's video. I think they have some beginner videos.