Any enters-the-battlefield abilities of the copied enchantment will trigger when the token enters the battlefield. Any "as [this enchantment] enters the battlefield" or "[this enchantment] enters the battlefield with" abilities of the enchantment will also work.

If an Aura is put onto the battlefield without being cast, such as by being created as a token, the Aura's controller-to-be chooses what it will enchant as it enters the battlefield. An Aura put onto the battlefield this way doesn't target anything (so it could be attached to an opponent's permanent with hexproof, for example), but the Aura's enchant ability restricts what it can be attached to. If an Aura token can't legally be attached to anything, it isn't created.

If the copied enchantment is a token, the token that's created copies the original characteristics of that token as stated by the effect that created the token.

Once you choose to create a token copy of an enchantment during the resolution of Ondu Spiritdancer's ability, that ability won't trigger again that turn, no matter how many more enchantments enter the battlefield under your control.

Each token copies exactly what was printed on the original enchantment and nothing else (unless that enchantment is copying something else or is a token; see below). It doesn't copy whether that enchantment is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, or so on.

If the copied enchantment has in its mana cost, X is 0.

If multiple instances of the ability are on the stack (perhaps because multiple enchantments entered the battlefield under your control at the same time), you will be able to create a token copy of an enchantment for only one of those instances. Once you do that, other instances will do nothing as they resolve.

If the copied enchantment is copying something else, then the token enters the battlefield as whatever that enchantment copied.