Spirit Highlands

The Spirit Highlands allows for the farming of Pet Fragments for all 5* Units. Each day 10 tickets are available to farm stages although this can be increased permanently through purchases in the main shop. Additionally extra tickets can be bought in bundles of 5 on a daily basis for gems. Each Purchase increases the cost: Generally it is recommended to at minimum buy 10 extra fragments per day, although some recommend 15.
 * 1st Purchase - 100 Gems
 * 2nd Purchase - 200 Gems
 * 3rd Purchase - 400 Gems
 * 4th Purchase - 800 Gems
 * 5th Purchase - 1200 Gems
 * 6th Purchase - 1600 Gems

It is recommended to clear every pet fragment stage with a 3* result as this allows them to be instantly completed in future to save time. The other stages can all be cleared with a 1* as there is no need to clear multiple times.

Rewards
The reward system is quite consistent: A full list of available pet fragments is shown below:
 * Stages ending in 2, 4, 7 or 9 provides 7 Honor Coins.
 * Stages ending in 3 or 8 provides 10 gems.
 * Stages ending in 1 or 6 provide a single pet Fragment
 * Stages ending in 0 or 5 provide 3 pet fragments.

Solutions
There are a couple of external sources with solutions to various Spirit Highlands stages:
 * Subreddit - Spirit Highlands Solutions
 * Website - Endless Frontier Data