  Close white dwarf binaries play an important role across a range of
astrophysics, including thermonuclear supernovae, the Galactic low-frequency
gravitational wave signal, and the chemical evolution of the Galaxy. Progress
in developing a detailed understanding of the complex, multi-threaded
evolutionary pathways of these systems is limited by the lack of statistically
sound observational constraints on the relative fractions of various
sub-populations, and their physical properties. The available samples are
small, heterogeneous, and subject to a multitude of observational biases. Our
overarching goal is to establish a volume-limited sample of all types of white
dwarf binaries that is representative of the underlying population as well as
sufficiently large to serve as a benchmark for future binary population models.
In this first paper, we provide an overview of the project, and assemble
reference samples within a distance limit of 300\,pc of known white dwarf
binaries spanning the most common sub-classes: post-common envelope binaries
containing a white dwarf plus a main sequence star, cataclysmic variables and
double-degenerate binaries. We carefully vet the members of these "Gold"
Samples, which span most of the evolutionary parameter space of close white
dwarf binary evolution. We also explore the differences between magnitude and
volume limited close white dwarf binary samples, and discuss how these systems
evolve in their observational properties across the Gaia Hertzsprung-Russell
diagram.
