My in-city bike is set up as a 1x7. That works fine and I don't feel the need for more gear combinations. In front I have a Surly single-speed chainring. It has tall teeth that hold the chain well, so I don't need a chain guide to keep the chain in place.
With a 10-speed cassette you'd need a narrower chain, and it might not work with an SS chainring. If so you'd need an ordinary chain ring and a chain guide of some sort.