Thats def the way to go to test juices. Make sure you get a drip tip too if your going to use the attys to test juices.
The atty I use to test juices on my E-Power is an HH .357 Hybrid, its an awesome atty, but is not cheap at all.
Id say your best bet is to just get a plain Boge atty or something. I just got a Boge 2.0ohm with some juices I ordered and it works well. Their reasonably priced.
For batteries there are quite a few vendors that carry them. I use the regular ones and also 14650 Hi-Drains.
If you do get them from MadVapes, make sure you get the right ones. They sell 3-4 different 14650 batteries. Personally I dont like the Ultrafire or Trustfire. I would buy the ones that just say E-Power replacement battery. They are the ones that come with the kit and they work well. The Ultrafire ones are more expensive bc they say they are 1300mah, but they really arnt. They are about 1050mah just like the stock ones.