OH btw how are you all finding these libs to add to the development kits? I am lost on these...
package manager (apt-get irrlicht-dev)
You're using Mint, which is based on Ubuntu, which is a Debian derivative. Debian uses the "deb" package format -- a standard way of packaging software and declaring all the necessary dependencies.
Unlike, say, Windows in which there is no such thing as a standardized way of distributing software, most Linux distributions stick to providing all software in a single way (although different distros use different ways -- there is no "there" there in GNU/Linux).
On a Debian-derived system, the package is the "deb" and there are several tools to use debs. The most fundamental one is "apt" and you'll see instructions for downloading and installing packages from the command line using the "apt-get" command. The apt-get command will select a named package from your configured sources and download that package and all other packages required to make it work, and install them. If you always use this tool, your system will never get in to a broken state.
If you start up your Mint system, open a terminal, and type "sudo apt-get install libirrlicht-dev" the system will find, download, and install the Irrlicht development package (which contains header files and link libraries) and the libirrlicht1.8 package (the runtime DSOs, or shared libraries) required to develop against Irrlicht. You can see more information on that package by using the command "apt-cache show libirrlicht-dev", and you can see what files were installed using the command "dpkg -L libirrlicht-dev".
The installation command must be run as the superuser (a privileged administrative user) because it installs the packages system-wide. That's what the 'sudo' command does.
These are all basic commands you just need to learn. There is a learning curve for any system, including the one(s) you already know. It's no harder to do things on a GNU/Linux system than on any other system, don't let your prejudgement fool you.
Tip: to find other development packages, for example, the SDL2 packages, use "apt-cache search libsdl2" to search. The standard Debian naming convention is to prefix a library package with "lib" and suffix a development package with "-dev".