If you are using a known good (original) cable and a known good wall charger, and still it doesn'tt charge properly, then there are many other reasons why your iPad is not charging, and you need to open it up to find out why. You need to follow the path of current to see where it is broken:
1/ The charging dock is defective and not passing the current like it should;
2/ The charging dock is fine but due to a fall, it moved and needs to be reseated on the board;
3/ The path is partially broken on the logic board which is malfunctioning. You will need the help of a trained technician to troubleshoot and repair this one;
4/ The battery bank is not holding a charge like it should. One good way to tell is if one or more of the batteries is swollen. But it could be defective and not swollen.
Not to sound discouraging, but to open the iPad and test all those, you may need a new dock connector and a new battery, and still may have not solved the issue. Plus you might break the front panel during disassembly.
If you feel up to it financially, and have the time to do it, let us know and we can guide you through the needed steps to minimize unneeded expenses and maximize chances of locating the fault. Or you can take it to a reputed repair shop and have it diagnosed first.
You can read through this guide to see what you will be up to if you decide to try the repair yourself.