have arbitrary Rocket League Credits NPCs from xingwang's blog

Your island will ultimately have arbitrary Rocket League Credits NPCs, similar to Gulliver or Saharah, who make a trip for some explanation.

You'll need to wander around to observe whoever may be halting in your town. Some of them generally show up in comparable spots. Gulliver, for instance, will be done for by the ocean side, and a trader like Label will be in the town square.

Any place you track down them, converse Buy Rocket League Items

 with them and see what they need — for sure they're selling, which can be restrictive things.