Your iPad is designed to improve system performance by caching data - and for this it will use available local storage space. iPad will usually automatically manage its available storage, deleting cached data as additional storage is required for other purposes. Sometimes, for older storage-constrained 32/64GB devices, that have very little available local storage, you may have to lend a hand...
Should you need to do so, cached Safari data can be easily purged. Depending upon the installed version of iPadOS, the path through settings may differ slightly:
- Settings > Apps > Safari > Advanced > Website Data > Remove Website Data
- Settings > Safari > Advanced > Website Data > Remove Website Data
Manually deleting cached data, as you have from iPad settings, will temporarily eliminate cached data. However, as you use your iPad, temporary data will slowly start to accumulate - again reducing your available free space. Unless you encounter a situation where you receive a warning about insufficient space, this is unlikely to be an impediment to use of your iPad.
With that said, it is generally recommended that you aim maintain at least 4-6GB of free space at all times - as your iPad needs some temporary space to complete many tasks. When performing system software updates, you may temporarily require more.
If your internal storage is full, or is insufficient for the task that you need to perform, your only option is to better manage the storage that you have - and delete unused Apps or unneeded data.
These support pages should prove to be helpful:
About storage on your device and in iCloud – Apple Support
What's the difference between device storage and iCloud storage? – Apple Support
Manage your iCloud storage – Apple Support
How to check the storage on your iPhone, iPad and iPod touch – Apple Support
Clear Other storage on your iPhone or iPad - Apple Support
“Offloading” Apps can be a helpful method of creating temporary space for a software update:
https://9to5mac.com/2020/01/21/how-to-offload-apps-in-ios-to-save-space-without-deleting-their-data/
External storage options can often help with managing limited internal storage. Depending upon your iPad model, the iPad will either have a Lightning or USB-C port - and may therefore require either an Adapter or USB hub to connect the USB Storage device. If your iPad has a Lightning port, you’ll need an Apple Lightning to USB3 Camera Adapter:
- Lightning to USB 3 Camera Adapter
https://store.apple.com/xc/product/MK0W2ZM/A