Standard: dual, add -an, quintal, add -in, generic plural add -en
The dual should be straightforward enough, it demarcates pairs, couples etc., no inherent magic of any kind.
The quintal was originally used merely to mark sets of three to five members, but has taken on several other meanings. It is now used as a form of paucal, denoting a small collection of things countable from a distance, as long as there are more than two members involved. Furthermore, it has taken on a role as a set-maker, e.g. tavin has taken on the additional meaning of "a pack of wolves".
The generic plural covers the situations where the size of the set is unknownor uninteresting.
blayatta
The best known trace of earlier or foreign pluralization-methods is known as the "tyan-construct".
tani -> tyan
skani -> skyan
skian -> skeìn
ciar -> ceìr