Translation:Aedilis praeter Comitium ac Forum basilicasque etiam Capitolium ornavit porticibus ad tempus
extructus in quibus rerum copia pars apparatus exponeretur.
As aedile he [Caesar] besides the Comitium, the Forum and basilicias, even the Capitol he furnished with colonnades set up for a while for displaying a pile of stuff, part of the booty he had amassed.
exponeretur: passive, subjunctive, imperfect: I guess the subjunctive here wants to emphasize that the colonnades were build for a purpose, to display some stuff of Caesar's.
apparatus: my translation of this as "booty", was a guess, for I was unsure just what Caesar was putting on display. Since it was put on display in temporary colonnades it must have been pretty impressive stuff.
copia pars: these words I think are in apposition.
I need a checklist like this: upon encountering a subjunctive, consider that it may be one of these: (list of subjunctive uses). The trouble is that I studied the uses of the subjunctive, in several lessons, some time ago, and I have not yet put the interpretation of them on automatic pilot, so to speak.