  We study the dynamical properties of certain shift spaces. To help study
these properties we introduce two new classes of shifts, namely boundedly
supermultiplicative (BSM) shifts and balanced shifts. It turns out that any
almost specified shift is both BSM and balanced, and any balanced shift is BSM.
However, as we will demonstrate, there are examples of shifts which are BSM but
not balanced. We also study the measure theoretic properties of balanced
shifts. We show that a shift space admits a Gibbs state if and only if it is
balanced.
  Restricting ourselves to $S$-gap shifts, we relate certain dynamical
properties of an $S$-gap shift to combinatorial properties from expansions in
non-integer bases. This identification allows us to use the machinery from
expansions in non-integer bases to give straightforward constructions of
$S$-gap shifts with certain desirable properties. We show that for any
$q\in(0,1)$ there is an $S$-gap shift which has the specification property and
entropy $q$. We also use this identification to address the question, for a
given $q\in(0,1),$ how many $S$-gap shifts exist with entropy $q?$ For certain
exceptional values of $q$ there is a unique $S$-gap shift with this entropy.
