tepid oriole
The main ways that people grind gems apart from the ones you mentioned are through event rewards, track rewards for collection book/ascension lines.
But if you want something that's more hands on, then you should first spend 600 gems to unlock gem trading in the market (If you haven't already). Then anytime you craft something rare, preferably flawless/epic/legendary rarity, sell those in the market for gems
tall notch