While Gentoo is certainly not an easy distro for linux beginners, it is certainly not impossible. If you're willing to be patient and want to learn, you can surely fix this problem. Your choice.
A couple of questions:
1) Do you use dhcp or static ip to connect to your network?
2) If dhcp, did the Gentoo install cd properly connect your network?
I've used a Linksys card with Gentoo before and had no problems. Here's what I did.
From a console: (commands are in " ")
1) "su" (enter your root password when asked)
This will give you root privileges which are needed for compiling a kernel and other configuration files editing.
2) "cd /usr/src/linux"
3) "make menuconfig"
At this point enable the tulip drivers (and the sub-options below it). I always built them directly into the kernel. This is done by using * instead of M. This way you don't have to worry about the modules being loaded at boot, as they load with the kernel. Now hit exit until you are asked if you want to save your config. Say yes.
4) "make && make modules_install"
This will compile your kernel and install any modules that you have asked to be compiled. When done compiling move to the next step.
5) "cp arch/i386/boot/bzImage /boot/kernel-whatever-you-want" (change whatever-you-want to the name you want your kernel to be remembered as. A word of advice. Change the name to something other than what you used when initially installing, that way if it doesn't work you can still boot from the old kernel)
"cp System.map /boot/System.map-whatever-you-want" (make sure it has the same name as your new kernel, for examle: kernel-2.6.11 and System.map-2.6.11)
"cp .config /boot/config-whatever-you-want" (again, same name as kernel)
6) If you have overwritten your old kernel then skip this. If you gave your kernel a new name then:
"nano /boot/grub/grub.conf"
and edit the kernel line so that it points to the new kernel name.
7) Reboot
Assuming that you use dhcp and have dhcpcd installed, your network should be up and running.
8) "ping
www.linuxquestions.org"
You should receive some info about packets and bytes. control + c to stop this.
Hope this helps