Can someone guide me how I can create a custom linux system in the easiest way? I would like to add programs and libraries of my choice on top of a base platform and offer it for free for download.
There is a difference between starting your distro vs. using libs/apps you need on top of base platform.
For the later look at gentoo, archlinux or lfs. The first two provide you a bare minimum 50mB core and a solid package manager. Then you can add apps of your choice on top of it. With gentoo you can also compile each of your package with your preffered choice of compile options.