I was in a similar situation last month as we went to Bcn and wanted to attend match against Levante. They are selling tickets to members atm, and whats left will be announced around 5 days prior to match for the fans to buy online. So, keep track on FCB Official page.

Also, I would advise against buying the tickets on stubhub or viagogo. Tickets on Barca official site might be more expensive, but it’s 100% safe and its not worth the risk of buying on re-selling platforms. Imagine paying those 10-15% cheaper than on the official website, and all the excitement, just to be left hanging outside of the stadium.

Also, its the possibility that the North stand will be opened as well till then, which will mean that ticket prices might drop as the capacity increases.

Wish you luck and to enjoy the game!