The effect of “Greed” only applies to cards drawn while “Greed” was active. If “Jar of Greed” is chained to “Greed”’s activation, “Jar of Greed” (Step 2) resolves and you draw 1 card for “Jar of Greed” before “Greed”’s effect (Step 1) was active, so no damage is inflicted during the End Phase. But if you chain “Greed” (Step 2) to “Pot of Greed” (Step 1), then “Greed” is active before “Pot of Greed” resolves, so the activator of “Pot of Greed” takes 1000 damage from “Greed”.
You can chain to the effect of “Greed” that inflicts damage.