There's a few things one has to remember when establishing such a group. While I love the idea and have sometimes fantasized about living in one (though my current lifestyle makes such a life impossible at this time), it's not without problems of its own that must be considered.
Keep in mind that I'm not saying establishing an actual Tribe is a bad idea; just that problems need to be recognized and accounted for ahead of time.
First of all, you're not going to be living exactly as our ancestors did. That's just not going to happen. The reason is simply because of the world around us, of which we are connected. The Tribe would have to buy property from the government it lives in and adhere to the laws of said country. An alternative might be to try establishing a micronation, but seriously, good luck.
One of the biggest reasons why you wouldn't be living as our ancestors did is because of the way the old Tribes interacted with one another. Based on some information about the time period and behavior that I've gathered from various bits, I've come to think that they were organized and operated less like modern Native American Tribes, and more like modern street gangs. Violent rivalries between Tribes were commonplace and likely based on fairly arbitrary reasons. Obviously in order for any sort of modern Tribe to work, that must be an aspect left in the past; any other separate Tribes are not to be regarded as rivals in any way. However, there should still be some sort of means to defend yourselves in case of an attack. (which doesn't have to involve killing the attackers).
One other thing. About those day jobs? Chances are there wouldn't be anywhere near enough time for everyone living in the Tribe to have such jobs, because there'd be hunting, wood gathering, farming, and repairing tasks going on pretty much every day. The bulk of the people living in any given village wouldn't likely have time to ever really leave because of all the work that would need doing on a daily basis. Obviously people can and should take shifts so others can have days off to rest, but "day jobs" should probably be the domain of a few select individuals who bring in money for everyone else, primarily to help pay any necessary taxes.
And finally, while such a lifestyle is likely very worthwhile and satisfying, you can basically say goodbye to most modern luxuries. Internet would likely be slow if it existed at all, and computers would likely be forever 10 years outdated. Electricity and other utilities would be somewhat problematic, though I will note that the farm I interned at was fully solar powered. Water can easily run out if a Summer is unusually hot, and a bad Winter can kill crops and livestock. Fire would be a constant hazard, and should be always kept in mind. If there hasn't been any rain for months, NO BONFIRES!! Health care would also be much harder to get, particularly in cases of mental illness.
There's probably dozens of other considerations that just aren't coming to me right now, but if they're not taken into account and prepared for ahead of time, the culture shock of such a lifestyle might be so strong that people who sign on might leave within a month. Such a life would not be any sort of utopia, even if the wonders of such a lifestyle make the problems all worth it.
I recommend looking into a Commune called Black Bear Ranch, in California. This is a community of people who've done something not unlike what you're proposing, but without the Pagan elements. Seeing how they've tackled certain problems might help give inspiration.
EDIT: One other thing, beliefs aren't really a part of community so much as practices. In the Old Times, there would have been plenty of diversity in what people would have believed about the Gods even in the same Tribe. The unity came from the fact that they all still would have attended the communal Rituals. Having disagreements in beliefs can actually keep discussions going, and keep the religion alive rather than stagnating. It only becomes a problem when the beliefs themselves become taboo.
