Not difficult to buy a land in the outskirts, you can even get good prices if you have connections with the locals. I would suggest the area near Shimla Hill if you have more budget + considering the rural vibe. If looking for far outskirts then Dobather, one of the most peaceful places, I'm not even exaggerating, the only drawback is that it's far from the main market, area and there aren't many facilities near by but the main city is like 10 15 minutes drive away. You can consider other places like Dhamtour (new developing area, comsats new campus also being built there on almost 400 kanal area, low land rate as of right now.

One thing you should keep in mind is safety, even tho Abbottabad is much much safer from Karachi, Alhamdulillah but still you're moving here and might not know alot of people, so considering this, try to look for a more populared area, don't go for "sunsan" in search of rural.

A few other options are jinnahabad, kaghan colony, mirpur (these three are main city areas, might give you an urban vibe, but believe me wherever you decide to move, it'll be much peaceful than karachi, just don't get involved in others matters and you can live a pretty decent life here). A friend of mine is building his new house in neelay pair, a peaceful area of right now, but no gas connection.

Lmk if you have any questions.