You have got the Photos syncing only from your 'favourites' photo album. Go to Apple watch app, select Photos, choose either to mirror your iPhone, or a custom setting. Choose syncing photos as another album, for example 'camera roll'. Then set your photos limit (mine is set to 40mb - it will tell you roughly how many photos this equates to). Choosing camera roll means all new photos taken will automatically sync to your watch, up to your specified limit.