I personally have pillars in /srv/pillar/tops_d and added the top file /srv/pillar/_tops/base/tops_d.top.
The top file includes relative paths from /srv/pillar/ with a dot instead of a slash:
base:
'*':
- tops_d.statefile1
- tops_d.statefile2
- tops_d.statefile3
- tops_d.statefile4
I do not use any commandline arguments specifying pillars, just {% salt['pillar.get']('pillar_variable') %} from the statefiles in /srv/salt.