I have already tried and tested this firmware. And I would like to share this file to you. This file is available on chainfire's official link. So I am not the original owner of this file, I give credits to the chainfire team.
You can root your Samsung Galaxy A3 (A300FU). I repeat this is for A300FU variant of Samsung Galaxy A3. Do not use this in other A3 variant. I am not responsible damaging your phone. I have tested this file in version 5.0.2. I haven't tested it yet on version 4.4.4, I am not recommending to use it on Kitkat version (4.4.4).
So here is the files that you needed to download
Root File with Odin --> SM-A300FU_CFautoroot_5.02.zip
Samsung Driver --> Download Here
"Extract to your desired folder"
After extracting, install the Samsung Driver first. Just keep on hitting next.
Flashing the root file
- Open/Execute/Run Odin.exe
- Click on AP
- Locate the root file that you downloaded
- Turn off your phone (follow instruction below)
- Press Volume DOWN + Home Button + Power Button
- Press Volume UP to proceed in Download Mode
- Let the driver install first