I also have Nigerian Dwarfs. This is what I have:
MADE IN THE USA!
It comes with numbers. You have to order the letters. Make sure you order the 5/16" letters.
I prefere green ink in a tube over the black in a jar. I make an unholy mess with the jar ink... it is thinner in consistency.
The smaller tool and letters are easier with the smaller ears. Even then, I wait until they are 6 months or so to tattoo. I was worried the smaller characters would be harder to read... 3/8 or 5/16, they are BOTH hard to read after a few years!
When you get to tattooing, secure their head as much as possible and squeeze so the pins go clear-through the ear. It is a pain removing the tool from their ear, which is why you really want to secure their head, but that is the only way I've had a tattoo last the life of the goat. I put ink on the ear, ink on the pins, and then rub the tattooed ear with an ink covered toothbrush.
For future reference, DO NOT re-tattoo an animal without contacting the ADGA... you CAN do it, but you need to notify them. An undocumented re-tattoo is a quick way to get DQed at a show.