O'Riley at Athenry Galway

[bcarragher]

I am tracing my great grandfather Joseph Patrick Riley (it is believe that it was O'riley and droped it when he arrived in South Australia) who married Edith Brine in South Australia in 1919.
He was born abt 1891 at Athenry, Galway according to his marraige certificate with his father being Martin.  His children always talked about him coming from Cork.  It is believed that he had a brother John and sister Mary.  I can't find a trace of him in the shipping records but i believe that he was traveling alone.

I would much appreciate any information or where to start reseaching as I have no knowledge of doing researching in Ireland