If you are used to using <ctrl>-<tab> and <ctrl>-<shift>-<tab> in firefox, chrome, etc, and want to have the same in gnome terminal, its a little tricky, but these commands should get things setup so that it works for you.

gsettings set org.gnome.Terminal.Legacy.Keybindings:/org/gnome/terminal/legacy/keybindings/ prev-tab '<Primary><Shift>Tab'

gsettings set org.gnome.Terminal.Legacy.Keybindings:/org/gnome/terminal/legacy/keybindings/ next-tab '<Primary>Tab'