Depends on how much data you want. The airport has a
vodafone shop in arrivals, and a few other retailers. Vodafone Total - 18€ gets you 3 gigs of 4G traffic + 500 min/sms to use locally (good for one month). If 1GB is enough, 13.49€ is the price.
I use a competitor, NOS, with similar rates and a similar price.