It's an MTK phone ( MT6580 ).
I managed to port and flash TWRP custom recovery by myself and it's working find. So I decided to flash SuperSU.zip with it. Everything seem to be working perfectly but after the flashing finished and I tried to open SuperSU app a message pop up with text "There is no SU binary Installed, and SuperSU cannot install it. This is a problem. If you just upgraded to android 5.0 you need to manually re-root - consult the relevant forums for your device!".
Please help me find a solution. I tried many version of SuperSU.zip already but the same message still appear. I also tried remove SuperSU app first before re-flash SuperSU.zip. I even tried to perform a clean stock rom flash before flashing latest SuperSU.zip and it's still the same.