ArchLinux with fluxbox or something similar will do.
But I would try upgrading to 256MB ram if you want to run something heavy like firefox.
https://wiki.archlinux.org/index.php/Official_Arch_Linux_Install_Guide
it's an easy to customize distribution and has one of the biggest user base among today's linux distributions.
If you have any questions, just ask. Two of the developers are personal friends of mine ;)