gt is the keyboard shortcut for :tabnext and gT for :tabprevious.
If you prefer the typical Ctrl + Tab, define the following mappings in your ~/.vimrc:
" CTRL-Tab is next tab
noremap <C-Tab> :<C-U>tabnext<CR>
inoremap <C-Tab> <C-\><C-N>:tabnext<CR>
cnoremap <C-Tab> <C-C>:tabnext<CR>
" CTRL-SHIFT-Tab is previous tab
noremap <C-S-Tab> :<C-U>tabprevious<CR>
inoremap <C-S-Tab> <C-\><C-N>:tabprevious<CR>
cnoremap <C-S-Tab> <C-C>:tabprevious<CR>