Healer, witch, cultist, priest, elementalist, warlock: "Shamans" can fulfill many roles, inspiring hope or fear, serving as either trusted advisers or feared bogeyman. More than even paladins or rogues, shamans differ from indivdual to indivudal, with almost no two the same.
Shamans make Deals. Not every shaman would phrase it this way, but ultimately, they've all made a bargain to trade away something of their own in exchange for power. Some are blunt demon cultists, happy to sacrifice souls or human victims for magic. Others are priests and ministers who give their devotion and worship, and receive abilities that help them tend to their flocks. Animist shamans make more complex bargains with several different spirits as the situation requires, but ultimately, the effect is the same.
Ultimately, it is hard to pin down any particular common "styles" for shamans, given their ability to draw on almost any track even without multiclassing. Certainly, those focused on healing and protection of the innocent make good use of Bastion and Force of Will, but more offensive shamans find themselves happy with Just Blade, Elementalist, or even Smiting. Tribal wise folk may incorporate Path of Rage or Path of Destruction (or, indeed, actually be Barbarians multiclassing for Incantation or Shaman Casting). Necromancers have been known to make dark deals with some of the entities haunting them from their birth for even more eerie power. A priest of a luck deity could, of course, utilize Fortune's Friend. If one were to look hard enough, one could probably find at least one shaman with every conceivable track filling their Shaman's Path.
While the ability to bargain with gods and spirits exists in all the sentient races, some take more readily to the shaman's path than others.
Elves of all stripes make talented shamans due to their natural insight and charm. The indigenous elves of the Americas often served as a priestly caste, and shamans are well-represented in such groups. Sanctuary elves become shamans to serve their communities with healing and communication magic. Elf wanderers may become devoted to deities of travel or roads. Perhaps the least common elves to become shamans are those integrated into human society, as they have intentionally left the ways of their people behind. Children and grandchildren of integrated elves, of course, may rediscover a connection with nature (or even find a way to bargain with the spirit of the city itself!) and follow the path once again, however.
Dwarves may be more naturally inclined to become tacticians, but shamans are still well-represented among certain dwarven cultures. The Carpathian dwarves have produced a number of zealous Orthodox priests wielding something more than mortal power against the monsters of the night, while dwarves of the Hindu Kush are led by wise elders who preserve their people's legends.
The innate charisma of gnomes makes them excellent shamans, for those who choose to pursue it. Like elves of a Sanctuary, they tend to focus their powers on protecting and guiding their communities.