If it's a Saturday game again you will probably not get a ticket. Swansea only have an away allocation of about 2k and I think, with folk wanting more points etc they will sell that amount out before any general sale.
Season tickets holders get points for how many years they have had season tickets, how many away and cup games they have attended. Then the away tickets go on sale to sth with a certain number of points. see link for an example. https://www.seagullstickets.com/documents/pdf/1718/AWAY_Arsenal.pdf...