Cultivation! Starting with a Loan

In a cultivation world where everyone struggles to improve, the male lead awakens a cross-world cave abode that lets him barter with the Myriad Worlds. He discovers that the spoiled Fasting Pills from his own world are high-energy nutrition pills in a wasteland, while even the lowest-grade talismans for Fireball spells are weapons of mass destruction. While others toil away at cultivation, he simply channels spiritual energy into himself to raise his cultivation level, reigns supreme in the wasteland, and sells immortality packages in the interstellar world. Before long, the cultivation world's style takes a sharp turn too: the Demon Venerable becomes obsessed with customizing mechs, the Saintess starts streaming the apocalypse, and the male lead stares at a spiritual vein converted from a nuclear power plant, lost in thought. What kind of immortal am I even cultivating?