  We conduct a reverberation mapping (RM) campaign to spectroscopically monitor
a sample of selected bright active galactic nuclei with large anticipated
broad-line region (BLR) sizes adequate for spectroastrometric observations by
the GRAVITY instrument on the Very Large Telescope Interferometer. We report
the first results for five objects, IC 4329A, Mrk 335, Mrk 509, Mrk 1239, and
PDS 456, among which Mrk 1239 and PDS 456 are for the first time
spectroscopically monitored. We obtain multi-year monitoring data and perform
multi-component spectral decomposition to extract the broad H$\beta$ profiles.
We detect significant time lags between the H$\beta$ and continuum variations,
generally obeying the previously established BLR size-luminosity relation.
Velocity-resolved H$\beta$ time lags illustrate diverse, possibly evolving BLR
kinematics. We further measure the H$\beta$ line widths from mean and rms
spectra and the resulting virial products show good consistency among different
seasons. Adopting a unity virial factor and the full width at half maximum of
the broad H$\beta$ line from the mean spectrum as the measure of velocity, the
obtained black hole mass averaged over seasons is $\log
M_\bullet/M_\odot=8.02_{-0.14}^{+0.09}$, $6.92_{-0.12}^{+0.12}$,
$8.01_{-0.25}^{+0.16}$, $7.44_{-0.14}^{+0.13}$, and $8.59_{-0.11}^{+0.07}$ for
the five objects, respectively. The black hole mass estimations using other
line width measures are also reported (up to the virial factors). For objects
with previous RM campaigns, our mass estimates are in agreement with earlier
results. In a companion paper, we will employ BLR dynamical modeling to
directly infer the black hole mass and thereby determine the virial factors.
