Hello everyone

I have been using linux for a year now, and I think it's time to try something more challenging. I am looking for a distribution that allows me to start at the very beginning and build a working system. In the past I used Ubuntu, Linux Mint, Debian, Mageia and OpenSUSE, now I am looking for a new challenge.

What I look for in a distro
- Being able to customize a lot of stuff
- Being able to make a system my own, and build it myself
- The first install, should only install the base system, then I can learn to build a system from there
- limited updates/upgrades
- Support for fglrx
- KDE
- Not Debian based, I looked into debian based distro's, and I just don't like them

I would appreciate any suggestions.

Do a total bare-bones / minimal install of CentOS and then compile everything else you want from source, step by painful step!

That describes every distro.
Sounds like Linux From Scratch.
Debian, I believe Crux, probably Gentoo and Arch (guessing), TenTenths informs us CentOS, and I doubt those are the only ones, but the number of distros that make such a thing easy are relatively few, since most distros are derivatives (slightly modified) of the main systems.
Stay away from rolling releases.
I confess my total and profound ignorance.
Irrelevant. Any GUI can be used on any system.

Any distro can be customized, though some DEs don't allow much customizing, for example Unity. Since you want to use KDE anyway that is a non-issue for you.
I am not quite sure what you mean with that, but if you want to build it yourself this points to the source based distros, Gentoo, CRUX, Lunar, ... , maybe to some extent Slackware or Arch.
Many distros allow a basic install from which you can build up. If learning is your purpose I would go for Arch, Gentoo, CRUX or LFS.
This definitely points to source based distros, where you can decide installed versions without running into dependency hell. You are even able to upgrade/downgrade at will with those distributions. For example, due to problems with Steam on distros that use GCC versions >4.7 I just yesterday have downgraded GCC from 4.8 to 4.7 and recompiled the complete system (took about 5 hours, not a big thing). Now everything is working without any problems.
Any distro.
Any distro.
Any source based distro, Arch, possibly Slackware.

Seeing your requirements I would think that you are a perfect candidate for Gentoo.

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Slackware certainly fits the bill as the distribution is pretty much "upstream" and does not come pre-customised.
Slackware also fits the bill in that a lot of software can be built from source and everything tweaked to your liking.
Slackware kind of falls into this category in that what you get on the installation DVD is the whole distribution - if you want anything else, it's either up to you to build it yourself or make use of the excellent slackbuilds (scripts which build and create packages from upstream source).
Slackware releases get few updates - mainly just security patches and some new upstream releases of stuff like web browsers. Many users tend to build their own kernels.
fglrx/catalyst support depends on your hardware, the kernel version and xorg version among other things. If your GPU is too old, you will have to use an older xorg version earlier release of a distribution in order to install the legacy driver. If you have a newer GPU then you shouldn't have any issues and can just download the installer from AMD and install it as you would in any distribution.
Slackware certainly has KDE.
Slackware is Slackware based.

Thanks for your replies.

Crux: I will look into this distro, anybody got any experience with this distro? does it break often?
Gentoo: looks promising, can this run for a long time without breaking, is there a big difference with funtoo, I like the idea of source-based
Arch: This distro isn't that stable, confirm/deny , I like how there isn't that much installed by default, is there something simular but more stable
Slackware: If I'm correct this is very stable, I will try this in virtualbox
Linux From Scratch: Not sure about this distro, can't find that much info about it, what makes this distro stand out?

For Arch Linux, it will be opposed to your demand for limited updates/upgrades. In Arch Linux as soon as a package new version is released, update is available. Hence there are lots of upgrades available.

It is also heard about Arch that if you keep regularly updated/upgraded then chances of breakage are less as compared to if you just upgrade few apps.

For Gentoo, I am using it alongside Arch, I can not say exactly, but in around two months period, I have never encountered any problem except a suspend issue because I haven't configured wireless yet, and wrongly choosing Libreoffice source code rather than precompiled binary as it took a very long time in compiling.

Also delta upgrade facility in Gentoo doesn't works.

For your requirements, I think Gentoo is good candidate. It is stable in spite of it is rolling release. All the things you mentioned from "Being able to customize" to "Not Debian based..." everything is there.
Just give some time in installing and configuring your hardware, os etc. Then try to choose binary file instead of source wherever possible to save your too long compile time.

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Linux From Scratch is not actually a distro. It's a project where you build a complete distro of your own from source code, starting with the kernel and working up, and so learn how everything works. I didn't have the patience for it and quickly gave up. Then there's the question of keeping it up-to-date by keeping track of all the software you use … you'd be trying to substitute for the complete developer team of a distro!

Arch is rolling-release and not very stable in my experience.

Slackware is very reliable and may be what you're looking for.

Gentoo I've never tested.

Take the test! Although they cover a limited amount of distros.

I would say: Slackware, Arch, Gentoo, LFS, Crux.

Used it for a while in a VM without any breakage that I didn't cause myself. Abandoned it because it doesn't support multilib (running 32 bit software on a 64 bit OS), which is sadly still needed for me.
I am using that as my main OS, not for long yet, but as with CRUX, no breakage that wasn't caused by myself (or 3rd party proprietary software, like Steam). Haven't tried Funtoo yet, so can't comment on that.
Arch is a distro meant for customizing it yourself and always running the latest software. This means also that you sometimes will get software that may contain a bug or two, since testing times are pretty short.

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Thanks for your replies, they are very helpfull to me.

Oke, did the test result is gentoo or slackware, I will try to install both in virtualbox, and check them out.

^ Yeah, that's the two I always get.

I am a little shocked that no one has suggested FreeBSD at this point.

One of the requirements is to have fglrx. Since AMD does not support the BSDs fglrx is missing on any of them, which disqualifies them right from the start.

Just shows how much I don't know about FreeBSD.