I have personally used "three filters" system. It's commonly available in Islamabad/Rawalpindi. Visit any nearby "hardware shop" and ask for "water filter with three filters". Price would be around Rs. 4K to 6K. Mostly, installation is either included or may take Rs. 200 to Rs. 500 to install. No need to install it yourself. Most hardware shops have contacts of people who can install it. They'll either send their own person or someone else who can install it.
There is no specific good brand for water filtration system. Brands are pretty much useless for local stuff. Three chambers are:
1) First chamber: remove thicker particles
2) Second chamber: remove fine particles
3) UV lamp
It's not install-and-forget. Keep the phone numbers of the person who installed the filter and the shop from where you bought it. After every 3~6 months (less or more depending how dirty your water intake is), it's your responsibility to call them and ask them to replace first two filters, check the UV bulb (replace if needed), ask them to clean the filter unit chambers too (wash with dish detergent). They'll charge some amount for it. I have seen such nasty filters without any upkeep that you can smell fungus from "clean" water.
My only suggestion is to get filter with all three chambers with solid color chambers (mostly blue or gray etc.). Do NOT buy transparent filter chambers, sunlight or even normal room light can give boost to algae/fungus growth. But do keep them clean, at the very least after every 6 months. Better if you do quarterly or monthly. Your health is in your hands.
If you are freak like me, cover all three chambers with thick cardboard and/or black plastic to filter out all lights to discourage any algae/fungus growth by cutting outside light.