There are two options to not have iCloud Photos use storage on your iPad.
One is to not turn on iCloud Photos on the iPad. Whether or not photos sync with iCloud and with other devices is a choice on each device. To turn it on, see: Set up and use iCloud Photos - Apple Support
If it is already turned on in the iPad and you want to turn it off, see: How to turn off iCloud Photos - Apple Support
The other option if you want to have iCloud Photos turned on in the iPad is to use the Optimize Storage option on the iPad to reduce the amount of space that the photos take. See the following from Set up and use iCloud Photos - Apple Support
Cloud Photos keeps all your photos and videos in their original, high-resolution version. To save storage space on your device, you can turn on Optimize Storage.
If you turn on Optimize Storage, iCloud Photos automatically manages the size of your library on your device. Your original photos and videos are stored in iCloud and space-saving versions are kept on your device. Your library is optimized only when you need space, starting with the photos and videos you access least. You can download the original photos and videos over Wi-Fi or cellular when you need them.
If you turn on Download Originals, iCloud Photos keeps your original, full-resolution photos and videos in iCloud and on your device.