Powers was a DC project and probably the only one of these more panned than Inhumans. Season 2 of JJ is set for 2018.
Of the ones you mentioned, Legion is the best, but it's also the least like a superhero show. Gifted is worth watching and there aren't many episodes to get you caught up.
Defenders kind of acts like the next season for its cast, so you'll want to watch Luke Cage before moving forward on that one. Iron Fist can be skipped. Agents of Shield gets a lot better. Season 2 and especially 4 stand out, but there are a lot episodes, so it's a big time investment. Agent Carter is fun and has a good message. Season 1 is better than season 2. It doesn't really have much bearing on the MCU, so it's not a must see, but it's quite solid.
And yeah, there really is a lot out there.