We develop a new method for representing Hilbert series based on the highest
weight Dynkin labels of their underlying symmetry groups. The method draws on
plethystic functions and character generating functions along with Weyl
integration. We give explicit examples showing how the use of such highest
weight generating functions (HWGs) permits an efficient encoding and analysis
of the Hilbert series of the vacuum moduli spaces of classical and exceptional
SQCD theories and also of the moduli spaces of instantons. We identify how the
HWGs of gauge invariant operators of a selection of classical and exceptional
SQCD theories result from the interaction under symmetrisation between a
product group and the invariant tensors of its gauge group. In order to
calculate HWGs, we derive and tabulate character generating functions for low
rank groups by a variety of methods, including a general character generating
function, based on the Weyl Character Formula, for any classical or exceptional
group.Comment: 76 page