You have a handful of ways to try out LXDE.

But I am totally new to those Linux things

We encourage you to try out Fedora LXDE

I’m not new, but I want to install something that comes with LXDE

Many distributions offer LXDE out of the box, such as LXLE, openSUSE, and Debian.

I have a Linux or BSD running on my computer, and I want to try LXDE

Sure. You can install LXDE easily. Please follow the wiki page to find out how to install LXDE for your distribution.

I want to buy a low-budget computer with LXDE

If you want to buy a computer, you can consider getting a single-board computer for a fraction of the price. Many single-board computers preloaded LXDE as their default desktop environment.

You could also consider getting a computer from a local computer recyclers and ask them to install Fedora LXDE, or Debian on it.

Although it could run on the computers with RAM as small as 256MiB, We recommend getting a computer with RAM of 1GiB or above for applications running on it, such as web browser, video player and office suite.

I would like to get the source code

If you are looking for the source code, we are hosting them in the SourceForge projects: