Unless you comprehend precisely what a VPN can and can’t achieve in specific circumstances, any reliance upon a VPN is perhaps ill-advised - as it likely provides negligible overall benefit and needless complication for you. "Free" VPN services are largely of limited benefit, may actually introduce privacy concerns - and should generally be avoided.
In most cases, a VPN only provides additional security and privacy for part of the communication path; unless you are running your own VPN Gateway service (if this means nothing to you, then you you won't be using one) it does not provide end-to-end security. VPNs have their place in the overall security/privacy jigsaw - providing just one element of the puzzle when used correctly - but are not of themselves a complete security solution.
You can perhaps stop here - and conclude that a VPN is unlikely to be of any use to you. However, if you a not completely lost at this point, you might wish to read on...
A VPN connection can only protect traffic between the VPN Client and the VPN Gateway. If you are running your own Gateway, while the VPN is active (and a no-split-tunnel traffic policy is applied) all traffic to your Gateway will have protection of the VPN tunnel between these two endpoints.
If instead you are connecting to a commercial VPN Service, your VPN traffic will be protected as far as your VPN Provider's Gateway - where it will be delivered to (and traverse) the internet without benefit of the VPN. As such, when connecting to an untrusted public WiFi, all of your network traffic will be protected over the least-trustworthy public WiFi connection - but receive no additional protection from where your traffic exits the VPN at the Gateway.
It is when using untrusted WiFi networks that Commercial VPN Apps may have useful utility - but you must consider that your unencrypted data remains visible to the VPN Provider. Choose your Provider with care - as not all are themselves trustworthy.
Also consider that much of your network traffic is already encrypted, by default, using TLS/SSL. That said, there are some network protocols (such as DNS) that do not have benefit of encryption - and this traffic can be intercepted or maliciously manipulated. This risk can be mitigated using DoH, DoT or ODoH protocols.
DoH and DoT are natively supported by iOS/iPadOS, but are not exposed via iPad settings; to configure and use these protocols you will need to use a third-party App - such as DNSecure. ODoH is also natively supported - but is only available to iCloud+ subscribers using Apple's Private Relay function.
Reputable “paid” commercial VPN services have no vested interest in your internet traffic beyond statutory obligations imposed by the authorities in whose territory in which they operate. Again, from a regulatory a technical perspective, this is no different to your ISP or mobile phone operator. Reputable commercial VPN services are fully and profitably monetised by service subscriptions.
Free or “low cost” VPN operators are funded differently. Clearly, these VPN operators have cost overheads that must be fully funded; such services are often funded through commercial advertising served via the VPN connection, or traffic analysis and data mining - this data being sold-on to other interested parties. Dishonest VPN operators may attract business with express intention of misusing your data - or to facilitate criminal activity.
Looking now areas where commercial VPN provides useful threat mitigation…
Assuming that your home wired/WiFi network is secure - and that other network devices using the network are trusted - use of a VPN within your local network offers no significant benefit. By contrast, public WIFi networks (such as Airports and Hotels) are high risk; other users of these networks can access and manipulate your network traffic - and it is here that a commercial VPN provides useful protection. Here, when using a VPN, all your traffic is fully protected from actors over the high-risk elements of the network path - between your client device and the VPN Gateway.
