So, what applications do I need. I think a lot.
I will start with a www-browser, and will install firefox.
In the Xfce guide, they simply say run the following command:
emerge --ask www-client/firefox
I tried that, and first ran into the message:
The following REQUIRED_USE flag constraints are unsatisfied:
cpu_flags_x86_sse? ( cpu-flags_x86_mmxext )
After searching, I found out, I needed to add the flag mmxext in the /etc/portage/make.conf file in the variable CPU_FLAGS_X86.
After this, there was another error message:
The following USE changes are necessary to proceed:
(see "package.use" in the portage(5) man page for more details)
# required by www-client/firefox-45.4.0::gentoo
# required by www-client/firefox (argument)
>=dev-lang/python-2.7.10-r1:2.7 sqlite
I used dispatch-conf to merge the files. (simply press ‘m’ to look at how the file looks after dispat-conf has merged it and use update (‘u’), to use the file it has merged).
After the use-files had been merged, firefox could be emerged.
I have not quite gotten the hang of searching with emerge --search yet. You search for a regexp, like apt-cache search. But, if there are many matches, you have to scroll back in the terminal with less.