[gii2]

Generally I would go with .NET Core - it is still in its infant stage, but by the time you have MVP it will be OK - Microsoft are throwing a lot of efforts in this direction.

For the mobile apps - Xamarin. You will still write C#, just use a different way of thinking.

Having the same technology stack in web and mobile will allow you to reuse skills one day when you build a team.

[jetti]

Just FYI, .NET Core is at 1.0 and already has a LTS version. It is definitely production ready now.