I am new to gentoo and I started installing it. I chose vanilla kernel and made it with genkernel. I now have a problem installing X. I get somewhere using vesa driver on xorg.conf however I think something is wrong since the background isn't very clear it looks like some static disturbance. I tried choosing nv as driver but it says that screen is not defined.

Then I tried installing new nvidia drivers with emerge nvidia-glx but the compilation fails. same for emerge nvidia-kernel. I am rather stuck with it - I have GeForce 6200

I recommend two things. First (if you haven't already) try posting in the Gentoo Forums. There are a lot of knowledgeable Gentoo people over there . Second, the proper driver to use is the one that comes with the nvidia drivers (not vesa or nv). I think you should post the output of your emerge nvidia-kernel. That will probably help in determining a solution to your problem. You also might want to try this: Gentoo Wiki: HOWTO Nvidia Driver Hope this helps!

Ok I got one step further - after some google I found a mentioning of
activating /dev/agp or something from kernel - I did so recompiled
kernel and the nvidia drivers compiled - however afterwards modprobe nvidia
gave an error and refered to dmesg where I had lots of errors for agp this and that.

It is a bit difficult to post the error log since I don't have the X running and have only
terminal on that gentoo machine...

I put M for that /dev/agp and there is also support for nvidia Force2 or something in
kernel 2.6.15 I try putting Y now and recompiling.

I've never really worked with Genkernel before so I really can't speak for it. I do have some advice though. When you run the Gentoo installation CD, run the command: lsmod. This will show you the modules that the liveCD uses for your system. The liveCD has pretty good hardware detection. Also run lspci to see if everything got recognized. With that in mind you should be able to compile your kernel with all the proper driver support that you need. I also run an Nforce2 motherboard so if you need me to, I can post my entire kernel configuration. Hope this helps.

Gentoo has the best documentation out of any distro I've encountered.
If you follow the NVIDIA Driver install guide from the gentoo handbook you shouldn't have any problems.
Just make sure you follow every step word for word.