Gold Nunchuk is Japan-only at the moment...I want to believe it will be offered here, but NoA really cheaps out on stuff that is offered...
Always register games ASAP. You get a few bonus coins. Also, if you do the "Intend to Buy" surveys, you can get a few extra coins and they do add up. Heck, once they release the Ambassador games, that's an auto 100 coins. If you haven't downloaded the free apps/channel for the Wii/3DS, you can get coins from them too...
Some third party games have started participating in coins too.