I don’t have experience with Tor on Android, so the below is just general commentary on Tor+VPN, not Android/Orbot specific.
My recollection is that the Tor Project doesn’t recommend using a VPN, but they also don’t categorically recommend against using VPN --> Tor
I’m not an expert, but I personally usually use VPN then Tor, I haven’t (yet) heard a compelling broadly applicable reason not to. Do you have clear reasons why you think it is a bad idea?
I don’t see a problem with [You] --> [VPN] --> [Tor] --> [Web]
I *DO* see risks and problems with (click me)
Don’t do this: [You] --> [Tor] --> [VPN] --> [Web]
Further reading on the topic for anyone interested in digging deeper: