The one rule of lifegain: sources feed payoffs A lifegain deck has two halves, and it is dead without both: Sources cards that gain you life, ideally incrementally and repeatedly (lifelink, whenever a creature enters triggers, upkeep gainers)
I'm not sure what the desire to play around with these sorts of effects is, because they're either immensely annoying, or they win on the spot with the right set-up
C Common Barrel Dragon X DARK Level 7 [ MachineEffect ] ATK 2600 DEF 2200 Once per turn: You can target 1 monster your opponent controls
Blissey #60 Pokemon Japanese Violet Ex Keep track of your collection value over time
After I was fairly sure Id put the Card Sleeve back in its box after the first day, I warmed to its approach
Fast forward fifteen years, and Kodama of the East Tree is here