Which office 365 for a small business

I'm struggling to pick which Office 365 sub I need and even which are available to me. MS seem to like making it hard to find out the specifics.

I see there is a small business option, but it appears to be renewal only.

I'm trying to drag this company into the modern era, but there has been a little kicking, and some muffled screams.

I need Office on one PC right now, with the probability of it becoming 7-10 (assuming they don't get spooked by some phantom problem).

I'd like to be able to add another machine quickly

I have no need for hosted exchange or cloud storage at this point in time, or the foreseeable future.

Someone please learn me.

Thanks