Mobile app? Amethyst. I can't say I've used iOS apps but I would go for Damus or Nostur. Obviously having never used them I can't comment really lol. But is assume they don't have primal features like 'sidebar of stuff you would like if you like bitcointwitter'.
Discussion
Jumble and Ditto.
Ditto is basically an exact twitter clone lol. Think you can get that as a PWA. But perhaps that is too annoying to give to someone.
I think Damus now comes with a wallet(?) so that would be my go to for absolute ease of use.