You don't need an IDE, but for larger scale projects, I find that IDE features do save time.

However, with some effort (and some rough edges), Emacs can be configured to do anything a "dedicated" IDE can do.

The main timesavers for me are navigation (quick open file, browse tree, jump to definition) and refactoring (find & rename references). Emacs can do all these. You might want to look into setting up ctags, speedbar, syntax highlighting & indentation prefs etc.

A quick google finds a couple of guides:

  * http://truongtx.me/2013/03/10/emacs-setting-up-perfect-environment-for-cc-programming/
  * http://tuhdo.github.io/c-ide.html

Which both seem quite approachable. I didn't see refactoring covered, but it's also do-able.