  We report an experimental study of the static magnetization $M(H,T)$ and
high-field electron spin resonance (ESR) of polycrystalline \MgGd, a
representative member of the newly discovered class of the so-called
tripod-kagome antiferromagnets where the isotropic Gd$^{3+}$ spins ($S = 7/2$)
form a two-dimensional kagome spin-frustrated lattice. It follows from the
analysis of the low-$T$ $M(H)$-curves that the Gd$^{3+}$ spins are coupled by a
small isotropic antiferromagnetic (AFM) exchange interaction $|J| \approx$
0.3\,K. The $M(H,T)$-dependences measured down to 0.5\,K evidence a long-range
AFM order at $T_{\text{N}} = 1.7$\,K and its rapid suppression at higher fields
$\geq 4$\,T. ESR spectra measured in fields up to 15\,T are analyzed
considering possible effects of demagnetizing fields, single-ion anisotropy and
spin-spin correlations. While the demagnetization effects due to a large sample
magnetization in high fields and its shape anisotropy become relevant at low
temperatures, the broadening of the ESR line commencing already at $T\lesssim
30$\,K may indicate the onset of the spin-spin correlations far above the
ordering temperature due to the geometrical spin frustration in this compound.
