Definitely worth playing. If you haven't played the first game, it will likely be slightly tougher to get a "good" ending. But it's one hell of a ride. And well, even the best ending is... underwhelming compared to the rest of the game.
Don't know which DLC you played for ME2, but make sure you play Lair of the Shadow broker and Arrival at least, before jumping to ME3. As for ME3, all DLC except Omega is pretty much mandatory.
But you don't necessarily have to play ME3 before playing Andromeda. Andromeda starts just after ME2, and then jumps to 600 years in the future, in another galaxy.
I played the DLC, and ME1 -- just missed the third somehow.