I want my LFS system as small as possible, I don't need gcc and whole glibc..and some other things. How can I do that?

uclibc will replace glibc, not sure about replacing gcc since you need that to compile anything else, although there's probably ways to make gcc a minimum install.

so system doesn't need glibc to run? can I compile in the last stage whole system by gcc from /tool and without installing gcc to /usr??

Yes you can use gcc from your chroot environnement
and if you really need a tiny system, you can also use busybox (a tiny bash and more)
to replace glibc, you have the choice: klibc, dietlibc but I think the best choice is µClibc

Oliv'

The system, as in the kernel, does not use a library, but most application programs do unless they are statically-linked (in which case the necessary library code is simply bundled-up inside of the executable). I don't know which alternative would be "smaller."

A default installation of both tools will bring in just about everything but the kitchen sink. (Ada, anyone?) But you can reduce them considerably if you try.

I need this system to work on Advantech PCM-5820, i need to run my own apps which will only transmit and receive some data through RS's and by network, to reduce cost i need to make the system as small as possible..and of course i don't need all stuff. But i need to be able to install some soft when i'll need it and be able to make some updates...so i don't want to install any of the pocket distro's. I'll try to make default LFS as small as possible...something about 40MB-50MB would satisfy me
so if you have any other hints i would be grateful
Thanks for help