You can make any piece of gear without traits for any level your skilled for as long as you have the material and style stone. To apply a trait to that same piece of gear requires that you research that specific trait on that specific piece. The "Special" sets in the game require that you have to have x number of items researched for each piece of gear you want to craft there. Below is a link showing all of the current craftable sets in the game. Take Death Wind set for example, it requires that you have 2 traits researched to make items for that set. So as long as you have any 2 items researched on each piece, you can make them all. You can ONLY make those items with one of those traits you have researched though.
The best thing to do is always make sure you are researching something. You don't need to work up the skill level to research an item. Working up the skill does allow you to add in skill points to areas that will let you research more than one item at a time though.
http://elderscrollsonline.wiki.fextralife.com/Set+Bonus+Crafting+Locations