Internal and iCloud storage serve different purposes. While you can store some data in iCloud, it is not a substitute for local storage.
What's the difference between device storage and iCloud storage? - Apple Support
Whichever iPad model of iPad that you choose, you would be well advised to purchase as much internal storage as your budget might reasonably allow - as internal storage (and other hardware) cannot be changed, upgraded or extended. The available internal storage is fixed for the entire life of the device. If you run out of internal storage for your documents, photos and other data, you will forever struggle and become a source of frustration. It is far better to have more storage than you need, than to need more storage than you have.
A good rule of thumb is to quantify how much data storage you will need - add a healthy margin - then double it. If you are unable to quantify your data storage needs, it becomes more difficult. Whilst I and others cannot cannot make definitive recommendations for your personal needs, objectively I would council against purchase of any iPad with any less than 256GB storage.
Within the Apple Support Communities we see regular tales of woe and disappointment when storage requirements are exceeded, necessitating replacement of the device; by contrast, we never see complaint of having too much available storage. It is relatively easy to fill limited internal storage space; perhaps consider higher tiers of storage as providing room for growth as your needs develop or mature - potentially extending the useful usable life of the device.
Consider also the functional differences between WiFi Only and WiFi+Cellular models of iPad. Only WiFi+Cellular models include GPS capabilities - which may impact any Apps or features that require accurate and consistent location data, such as Mapping. Purchase of a WiFi+Cellular model does not commit you to using Cellular connections, but provides this flexibility should it be needed. WiFi Only models of iPad have no Cellular or GPS functions at all.
