If Ashling leaves the battlefield after you've cast an Elemental permanent spell and paid its evoke cost but before that spell resolves, the permanent that spell becomes will still have evoke when it enters. As such, the triggered ability represented by evoke will still trigger, and when that abiltiy resolves, you'll still have to sacrifice that permanent.

If the copied permanent had {X} in its mana cost, X is 0.

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as an evoke cost), add any cost increases, then apply any cost reductions. The mana value of the spell is determined by only its mana cost, no matter what the total cost to cast that spell was.

The token created by Ashling's last ability copies exactly what was printed on the original permanent and nothing else (unless that creature was copying something else; see below). It doesn't copy whether that permanent was tapped or untapped, whether it had any counters on it or Auras and Equipment attached to it, or any non-copy effects that changed its power, toughness, types, color, and so on.

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

If you pay the evoke cost, you can have the creature's own triggered ability or abilities resolve before the evoke triggered ability. You can cast spells after that ability resolves but before you have to sacrifice the creature.

If the copied permanent was copying something else, then the token enters as whatever that permanent copied.