Do I have to attack in order to use Togekiss' "Precious Gift" Ability?
No, the "(after you attack)" text is just a reminder that your attack happens before the end of your turn. You can still use Precious Gift even if you don’t attack.
Source: Obsidian Flames FAQ Addendum; TPCi Rules Team (2023-08-10)

Relevant cards

Note: All applicable cards may not be listed below.
SV3_85
SV3_85