It sounds like you're encountering a common issue where the Gambit Seal isn't showing up in your Triumph submenu or the legacy seals menu. This can sometimes happen due to a glitch or because the game hasn't fully updated your achievements yet. A quick solution that might help is to check for any pending updates for the game or to log out and then log back in to refresh your account status. Additionally, I'd like to suggest considering a Gambit Carry - https://wowvendor.com/shop/destiny-2/d2-pvp/gambit/. It significantly accelerated my progress, allowing me to match my friends' levels swiftly. But, it's essential to weigh whether it's right for you, given that it might not be a fit for everyone. Each player's available gaming time varies, so take that into account before deciding.