actually most of the life gain cards aren't really needed just play Overgrown Estate in an otherwise near mono black deck (with maybe Rampant Growth and Orim's Chant or so), with Sungrass Eggs, and Praeries to cast it.
Here's how a lich deck usually plays out: find lich estate with insidious dreams, while you disrupt their game plan with discard and other black cards. Then drop the 2 enchantments, float 1B, sac your lands for lots of cards, play a sickening dreams for 20.
You could also combo Lich with Transcendence, and mana burn (pay life) for cards, but overgown estate costs only half as much as Transcendence, and is prolly more effective.