Depends if you want to do a mileage run or a segment run. Or... what is your starting point, what do you want to achieve and when do you want/need to achieve it?
For mileage run, either wait until summer offers come, when SK sometimes puts business class for sale at ok prices. It might be a bit expensive for a youth, though. They sometimes have long haul plus tickets during the year at ok prices, too. Try to add a creative routing, so not with hub as starting point. For medium and short haul I can recommend flying to HAM, TXL, GDN, BRU or AMS, as they often have relatively cheap plus tickets. And the flights are very short. All those airports have lounges for *G with the exception of GDN, as SK remains a bunch of cheapskates. Subscribing to their newsletter and keeping an eye out for offers, also helps.
It might even be profitable to fly with certain partner airlines on long haul flights as earnings at SAS on those segments sort of force your MR to be outside of SAS. I will soon embark a CA flight to SGN in C which I booked as error fare. It should earn me 110% mileage (or about 15000 miles) and a seat in the C-cabin for about 5000NOK and includes 2 SK legs in Plus as well. I also had an AC a few years back, with flights to Lima, Peru. It was great fun to visit Peru and I earned, at the time, a generous amount of miles on an economy ticket (75 or 100% I think). The ticket was also about 5000NOK.
Segment running might be equal. It's not recommended to have domestic flights in Norway, as you pay a load of extra taxes there. In fact, a one way flight in Norway may cost more than a return to HEL from OSL, for example.
Be aware of Widerĝe flights when flying to/from/in Norway, as they may have different point earnings or may not count towards segments earned. A pity, really, as I like Widerĝe better than SAS. The same goes for any other partner that operates codeshares with SAS (mind, I'm not talking CityJet or SAS Ireland, which operate as/for SAS. They should be ok as SAS flights and count as legs).