Otherworldly Lord: I Bought Elf Twins from the Start

[Reborn + Another World + Farming + Lord + Character Growth + Body Tempering + Elves] Lin Feng transmigrates to another world by chance and becomes a noble lord in a remote region. He obtains a Plunder System that grants him points as he grows stronger, which he can spend to steal other people’s skills. Thus begins Lin Feng’s path to kingship.

He buys a pair of elf twins, makes a contract with a witch, saves a succubus, and meets a mermaid princess...

He grows stronger through constant plundering, uncovers his family’s curse and secrets, expands his territory, strengthens his nation, and becomes lord of the world.

(The protagonist is physically invincible and also practices magic. He takes his time building his strength early on, then starts developing his power base later, stockpiling provisions and biding his time before claiming the throne.)