I like the way this is headed, with white also having tons of access to life gain
shenanigans. First off, I would capitalize on the life gain with extra life gain win cons like
Felidar Sovereign - it:s always nice to have multiple paths to victory. Secondly, I would throw away mana rocks like the signets, since you have access to green. Replace the rocks with ramp spells like
Farseek or
Skyshroud Claim, depending om how heavy you lean towards green of course.
EDIT: I see you already have
Farseek in the deck, my bad. Also, I wouldn't include the life gain dual lands, the cons outweigh the pros by a large margin.