Dragon Gate iPPVs can be ordered through Nico;
https://secure.live.nicovideo.jp/event/dragongate it's not that hard tbh, the Nico sign-up's in English and navigating the iPPV purchase page is fine if you're OK with google translated pages. They accept debit and credit card (although some people's banks block payments to Japan unless you expressly tell them not to), but also you can use web money points that are purchasable digitally from Play Asia;
http://www.play-asia.com/webmoney-2000-point-card/13/706xmv
As for other promotions, they either air on Samurai TV, GAORA or G+ - of the three only Samurai has a streaming service (a subscription channel on Nico), but unfortunately it's only open to Japanese customers. It would be amazing if they allowed non-Japanese fans to subscribe, as it's about the same price as NJPW World and carries a ton of promotions (BJW, AJPW, NOAH, Sendai, Ice Ribbon, Michipro, etc).