...sortof hate the barbarian costumeing standards... delineateing a separate "race" by clothing alone is a terrible idea...
Be that as it may...
General useful guidelines:
Non-finished edges- Hemming and finished edges should be kept to a minimum, this is a mark of higher-craftmanship and tools.
Rough materials- That is, non-refined fabrics and leathers. Low threadcount. Natural, breathing materials like hemp, cotton, leather...so forth. It shouldnt look like it needed a machine to have been produced. Avoid metal hard-ware for closures.
Non-standardized construction- That is, dont work from set patterns. OR try and fake not working from set patterns. No right-angles, no fine-tailoring... Think organic shapes.
There really is not any great way to go about it that dosnt require some crafting effort (you have to start somewhere, just dont be intimidated, you can do it, it just isnt going to be POOF overnite accomplishment) ... just tossing furs on yourself is probably not going to get you any farther than you presently are... raising the bar comes with work. but, still, check this stuff out...
Examples
-Note the difference between the wildlings and the non-wildlings.
Rough hewn, simple shapes. Not shiney, not clean. THis is all easy to construct stuff.
Of if you want to look at the more classic fantasy angle... theres some metal used here, but a lot of the design is based on all natural materials, letting the nature of he material be the star and not trying to refine it into something else. Texture, earth colors (even most of the metal is kept in the warm family)