No Elven Mystic available, but that part of Standard seems to be permanently over. However, there is several fairly efficient manaproducers in the format, like Servant of the Conduit and Rishkar, Peema Renegade and then there’s these two:
There’s also Kiora, Master of the Depths, which might work, but I wouldn’t bet on it.
So, how do we keep going with the first ability? Well, here’s an idea: The iconic creature for green is hydra. Make a larger one each turn.
Just a sick, sick idea on how to abuse Sorin, Grim Nemesis and the new Emrakul.