So being a no caste foreigner is better or worse than a low caste? :S I guess it depends on a lot of factors but...

It always comes down to the perception of how useful you could be. Do you look like you could have valuable connections? Do people look at you and think this person probably has money/smarts/connection/anything else of utility? Maybe you are exotic or good looking enough that they want to associate with you to increase their own standing in their own tribes?