Vim's default tab completion is horrible. Type :tabnew <Tab> in a folder with multiple filenames, and it will fill in the first available filename. Hit <Tab> again, and it will fill in the next filename. Rinse and repeat. This is NOT a viable method for a folder with hundreds of files. (You should try this so you know just how much of an improvement my suggested change is.)
Open your ~/.vimrc (or ~/.config/init.vim if you use Neovim) and add the following lines:
" get us bash-like tab completions:
set wildmode=longest,list
You should also type :help wildmode to read a bit about it.