You Do Need power plug adapter while traveling from Tuvalu to Gabon.

Here is Why You Need An Adapter

The outlet and plug type used in Gabon is C and in Tuvalu is I. This is how they look like.

Tuvalu

In Tuvalu, outlets of type I are in use.

Type I

Gabon

In Gabon, outlets of type C are in use.

Type C