Hi
The battery charge on Apple Watch will reduce over time, even when it is turned off.
It is possible that your watch was stored for some time before you received it as a gift. Your Apple Support Communities profile indicates that your watch has watchOS 1.0.1 installed. That software version was released in May 2015 and was followed in September 2015 by watchOS 2.0.
For the latest features and the best performance, update both your iPhone and Apple Watch to the latest software versions (presently iOS 9.2 and watchOS 2.1). Instructions for updating the software are available here:
- Update the iOS software on your iPhone, iPad, or iPod touch - Apple Support
- Update the software on your Apple Watch - Apple Support
More information about charging your watch:
Check your battery and charge your Apple Watch - Apple Support