There’s only a limited amount of stuff you can do without a Mac.
You can’t buy a license to run MacOS in a VM like you can for Windows, and iPad stuff is really basic.
Ultimately you need Xcode to build an iOS app.
One good thing is you no longer need to be a member of the $99 developer program whilst learning - you can install any app you’re building on a device and self sign it. You only need membership to submit your app to the store.
There’s plenty of cheap Mac Mini’s available used that would allow you to learn.