Is the iPad that you had bought for a profit from the local tablets wholesale store acting up and not letting you to update the device? Are you getting error messages on insufficient storage space while trying to update the operating system or the apps that are installed in the device? If yes, you will have to clean up the device and free storage space in it for the update to go through.
You will have to find out the exact amount of space that is left in the device to know the amount of space that you will need to free. This can be done by checking the total memory usage of the iPad. To check the total space usage of the device, you will need to select Settings > General, and then Storage & iCloud Usage. At the top of the screen, the amount of used and free space available in the device will be displayed. Below that will be displayed the amount of your iCloud space.
There are no hard rules on the amount of space that you need to leave free on the iPad, but if you are looking to free space so that you can capture new images and videos without worrying about storage limitations, you will need to free at least 1 GB of space in the device. It would be better if you can leave about 2 GB of space in the device so that you do not need to free space on the device frequently.
After finding the exact amount of space that is left on your iPad, you can plan about freeing the space. For this, you will need to find out the apps that you do not use much and is wasting space in the device. To know this, you just need to tap on Manage Storage option and the device will display a list of all the apps installed in it with details on the amount of space consumed by the apps. You can get rid of the unnecessary apps in the device to free up space.
After getting rid of the unused and unnecessary apps, you can check the device for free space and if there is not enough space, you can move forward to images and videos. Tap on the Photos & Camera app to see the details of the space used by it. You need consider the space used only by Photo Library as it is the one that store images locally on the device. If you find that more than 1 GB of space is used by the Photo Library, you may move the files to the iCloud or some other storage device, and then delete the files from the iPad and free up the storage space.