INSTALL SYSTEM DEPENDENCIES

This is the short list of dependencies you will need to start your server up from a base EL7 install:

$ yum install curl policycoreutils openssh-server openssh-clients postfix

ENABLE SERVICES

The server will need postfix for messaging and ssh for git and management. Here is how to configure this:

$ systemctl enable sshd
$ systemctl start sshd
$ systemctl enable postfix
$ systemctl start postfix

SETUP FIREWALL

Add HTTP, HTTPS, and ensure that SSH is correctly setup.

$ firewall-cmd --permanent --add-service=ssh
$ firewall-cmd --permanent --add-service=http
$ firewall-cmd --permanent --add-service=https
$ systemctl reload firewalld

INSTALL GITLAB-CE

Download, install, and configure gitlab-ce:

$ curl -sS https://packages.gitlab.com/install/repositories/gitlab/gitlab-ce/script.rpm.sh | sudo bash
$ yum install gitlab-ce
$ gitlab-ctl reconfigure

FINAL STEPS

This should yield a functional server, last thing is to visit the site and create your 'root' password, which will grant you a Administrator level account that can be used to configure the server further.