The Improbable Bulk
Join Date: Jul 2005
Location: Wilkes-Barre, PA
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There is no real increase in complexity between a 1x5 and a 1x9 so, I would suggest looking at 1x8 or 1x9 simply so that you can use a cassette instead of a freewheel, and use more modern components.
Even if you go with a 1x8, and ignore the smallest gear, you would probably end up with a higher level of component, and be happier with the result.
To get the widest range of gears, just look for a cassette that has the largest and smallest cogs, and a rear derailleur that is rated to handle that range... then pick a chain ring to give you the gear range you need. This is personal taste, but I would choose based on what gives you a low enough gear for the riding you need to do. The highest gear will get you up to a certain speed, then if you are going down hill, you simply coast when you get above that speed.
You can do a 1x7 using a cassette if 7 is really as high as you are willing to go by using a spacer, so that is as low as I would suggest. But, I really see no reason to go with 7 when 8 is just as easy to build, and it may be difficult to find a reasonable quality shifter for a 7 speed configuration.