First, in considering iPad models, you need to be aware that there are two basic choices - namely WiFi Only (no cellular capabilities) and WiFi+Cellular. In purchasing a WiFi+Cellular model of iPad, you are not committing yourself to needing a Cellular Carrier plan - but are preserving the opportunity and flexibility of doing so at a later time.
Also be aware the only WiFi+Cellular models have GPS location functions. WiFi Only models do not have any built-in GPS capabilities.
The potential need for GPS is one of the many reasons that some users choose a WiFi+Cellular model - even if having no need or intention of using Cellular.
Whatever model of iPad you choose, you would be well advised to purchase as much internal storage as you can afford - as internal storage 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 cannot make definitive recommendations, personally I would council against purchase of any iPad with any less than 256GB storage - 512GB or greater offering a greater level of safety.
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.