My guess is that Facebook or some other social media group chat or something along those lines would be the best way to start a group.
As for clothing and equipment- if people have never skied/snowboarded before, I would suggest renting the first time or two to make sure its something you like and want to stick with before buying. Clothing, in my opinion, is get a jacket not too heavy but big enough that layers can be put on underneath. You'd be shocked at how hot and sweaty you get once you start getting the hang of it! Gloves or mittens are the important part, having waterproof ones makes a world of difference.