I would build a machine, that has the capability of launching small metallic balls in every direction at once, almost like an explosion.
I would then have 1000’s of small metallic balls made.
The inner nucleus of the balls would be made of a soft man made material, such as porcelain or some other similar material, about 5 grams or so.
The inner nucleus of the balls would then be coated in a harder man made material, and would then have many other layers, all of man made materials, each layer harder than the last.
The balls will ideally be magnetized, or perhaps even mildly radioactive.
The very outer layer would be a thick layer of titanium, and engraved and indented on the surface it would say “I got here first” on one side, and kind of map on the other side.
I would then hitch a ride in to space, and have my machine launched in to space. The machine would be programmed to fly out of the solar system, and once well outside, it would open up and explode.
The metal balls would be shot out in all directions, and eventually end up some place. Maybe roasted in a sun, or lost in a gas giant, or maybe some will find their way back to earth. Maybe some will just drift in space forever, and maybe, just maybe, one or two may end up in the hands of a Zorlaxian farmer.
I think 4 million would probably cover it.