Most iPhone users don't need to buy additional hardware. Your iPhone can share its cellular data with your iPad through a feature called "Personal Hotspot." Your iPhone acts as a mini Wi-Fi router.
If you work remotely or travel frequently with multiple devices, a dedicated "pocket Wi-Fi" device is superior for stability and battery life. buy hotspot for ipad
Heavy data users, international travelers, and connecting 10+ devices at once. Most iPhone users don't need to buy additional hardware