If the shul doesn't have a full minyan at the time when Selichot is supposed to start, and waiting for a minyan to gather before starting is not an option, what are the rules for what you say or don't say before the minyan is complete, and once the tenth man arrives?
Say Ashrei and continue Lecha Hashem haTzedaka. If a Minyan comes during those points, Chatzi Kaddish is said provided some pesukim were said while the minyan was there. Mateh Efraim 581:17, Elef Lemateh. It is somewhat mashma that when the pesukim end and the main selichos start, you wouldn't say chatzi kaddish. If a minyan didn't come until the end, some selichos should be said together to say kaddish shalem.
The 13 middos or any reference to them are not said without a minyan (Matte Efrayim 581:21)
Aramaic selichos are not said without a minyan (581:21)
(I don't know the source of saying Elokeinu... before the selichos or why we skip it w/o a minyan, but that's what people do.)