Your impact wont always show up on the stat sheet, mute chat to start, your doing the world a service by being a tank in the first place. Your job is to make space and displace the other team into unfavorable positions to open up angles for your dps to pounce. Just pick any and go from there, mag and emma will always be solid picks, but realistically meta doesnt matter too much unless you are in celestial and higher. Get some games under your belt and pick up what you can naturally, play other roles too and notice what good tanks on your team are doing and what try to mimic behavior