You need to understand the difference between iPad and iCloud storage, and it seems that you came to the forum from that support document. The storage on the iPad cannot be increased, except to delete unwanted or unused content. There is minimal content that you can remove to free content, but you can go to Settings>General>iPad Storage to see a graph of what things are taking up storage on the device. It should also give you the option to Offload any unused apps. When you use iCloud Photos, that puts your Photos in iCloud, but also keeps a copy synced to your device. You can change the resolution of the photos you save on your device, but your best option is to import the photos from your iPad to a computer for storage, give the low amount of space you have on the iPad.