  We study a systematic improvement of perturbation theory for gauge fields on
the lattice; the improvement entails resumming, to all orders in the coupling
constant, a dominant subclass of tadpole diagrams.
  This method, originally proposed for the Wilson gluon action, is extended
here to encompass all possible gluon actions made of closed Wilson loops; any
fermion action can be employed as well. The effect of resummation is to replace
various parameters in the action (coupling constant, Symanzik coefficients,
clover coefficient) by ``dressed'' values; the latter are solutions to certain
coupled integral equations, which are easy to solve numerically.
  Some positive features of this method are: a) It is gauge invariant, b) it
can be systematically applied to improve (to all orders) results obtained at
any given order in perturbation theory, c) it does indeed absorb in the dressed
parameters the bulk of tadpole contributions.
  Two different applications are presented: The additive renormalization of
fermion masses, and the multiplicative renormalization Z_V (Z_A) of the vector
(axial) current. In many cases where non-perturbative estimates of
renormalization functions are also available for comparison, the agreement with
improved perturbative results is significantly better as compared to results
from bare perturbation theory.
