The Gemini tablet line performs factory resets and firmware updates with an SD card. Performing a factory reset requires writing files to an SD card with a computer, then starting up the tablet with the SD card present in it. Be aware that it will erase all data on the tablet, but with it in a boot loop, that may be a moot point.
Knowing the specific model number of your tablet is critical. Flashing the incorrect information can cause worse problems than you are encountering now. Rather than send you to the D7 GEM7007 page, I will give you the general page that leads to all the possible tablet results and directions. Look for the link that matches the Model Number, not just the name.
Factory Reset Original Firmware ROM Image Flashing Instructions
You will most likely need:
An SD card appropriate for the tablet (SD, MicroSD, Etc)
A reader for the card for your computer (Attached reader will handle SD and MicroSD)
The ability to get the Tablet to completely turn off to start the process.
The first two can be purchased. The last one is up to whether the tablet has a hardware fault. If the tablet has any kind of broken hardware inside it (wear and tear, aging, or damage) the process may not work. In the event of hardware failure, replacement under warranty or without warranty may be the best solution.