Mulligans
General Mulligans
Like I said before, look for your early hits to start generating board and card draw, or look for the hits to play early threats. I've dropped an Amirdrassil turn 1 and dominated from the start, naturally. Generate as much recurring draw as you can with Braingill and the Amalgams. Once you start shuffling the rest plays itself, as long as you have the draw to back it up.
Aggro Mulligans
Look for these cards ASAP. The more you can outrace them the better.
Midrange Mulligans
You can play this like aggro, their threats will be big, but you can usually outboard them.