I just put on index downtube shifters on my latest commuter build. They work well.

If you want something on the handlebars, the kind of bars you have make a difference. For flat bars, I'd go with thumb shifters. The choices are tougher with drop bars as I'm not aware of any inexpensive or even reasonably priced bar end shifters. So I'd go with downtube shifters if you have drop bars.