TL;DR: Get up and running with a Linux / Windows laptop. Save up for a used Macbook Air 2012 while you learn and switch to OSX ASAP.
You’re in a tough spot. I know because I was you in Spring 2016.
The first question you need to ask is yourself is “what’s my end game?.” If your end game is to become a developer that writes ASP.NET OR C# apps - buy a cheap Windows machine. For everything else, keep reading.
I would suggest picking up a cheap Linux PC. If it’s just for learning how to code, you don’t need much in terms of performance. You could use a Windows PC, but you’re probably much better off using a Linux machine. Why Linux? Because if you’re serious about becoming a professional developer, at some point, you will have to learn how to use a terminal. Bash is the terminal that ships with both Linux AND OSX. When you land your first job, chances are they are going to give you a MacBook Pro. Chances are everyone around you is going to be using a MacBook Pro, too. If you can already use a Mac and Bash you will be one step ahead.
If you decide to roll with Windows, that can work too. You just need to install a Cygwin and a terminal emulator. Cygwin combined with a terminal emulator will allow you to use most of the native Bash commands in a Windows environment. For the record, that’s how I got my start. I was running Windows on a Lenovo laptop. I used a terminal emulator named Babun. The great thing about Babun is that comes with Cygwin installed. So you can avoid the headache of installing and configuring Cygwin. Just install Babun and you’re ready to rock.
While you’re learning via Windows or Linux, try and save up for used Macbook Air 2012. As soon as you can, switch to Mac.
Some people will probably disagree with my me because they hate Apple. I used to hate Apple, too, until I started teaching myself web development. But I learned quickly that Mac is more or less the defacto OS for web development outside of the ASP.NET community. In the vast majority of web development tutorials, especially frontend tutorials, the lecturers are running OSX. Following along using a Linux machine is doable, I suppose. I know from experience that following along using a Windows PC is either difficult or impossible.
Furthermore, with respect to frontend development practically every popular tool supports OSX out of the box. Some can be configured to work with Windows or Linux, but in many cases, there is no support. You’re even handicapped working with designers if you’re on a Windows / Linux machine because of the rise of Sketch.
So, final words, get started with whatever you can and switch to Mac ASAP unless you specifically want to develop for .NET.
Regarding Chromebooks. It’s probably the worst option because you’re locked into the Google ecosystem and Chromebooks simply are not designed for software development. However, you could still get pretty far using a Chromebook and a cloud IDE that comes with a prepackaged development environment. If you end up going that route, I recommend Cloud9. It’s free and you spin up a fully-functioning development environment in minutes.