  We provide a systematic way of calculating a quiver region associated to a
given exceptional collection, which as an application is used to prove that
$\mu$-stable sheaves represented by two-step complexes are Bridgeland stable.
In the later sections, we focus on the case of even rank $2$ instantons over
$\mathbb{P}^3$ and $Q_3$ to prove that the instanton sheaves, instanton bundles
and perverse instantons are Bridgeland stable and provide a description of the
moduli space near their only actual wall.
