It wouldn't hurt to link the gift to a product made by the company. That's easy if the company is Mattel or Hershey. For a fast-food company like McDonald's, gift certificates may be in order. The easiest way is to transfer shares you already own. Mutual fund companies and brokers usually can explain how to set up a custodial account.
Parents often name themselves as custodians.
You can also buy a few shares of a company your kids know and like. If your spending limit is higher, buy two shares, or five or 10. That involves buying stock directly from the company. But shop carefully. Some companies require high minimum investments or impose stiff fees.