As noted, basements vary. Before buying a house, make sure the building inspector has issued a report on the basement, and any flooding reports from this or nearby homes. If its on flat land, or even a slight valley, I'd expect at least some moisture during rain storms, and seldom but extra heavy storms can overcome any drainage.. If its in a development and has storm drains, they can back up into the basement even if it is well drained.
Storing valuable non replaceable items in a fire proof and waterproof case is a good idea. Dryers are good to keep air dry under normal conditions, but are worthless if you are suddenly flooded. Sump pumps are also of limited value, since you often lose power during the really big storms.
Homeowners should cover replacing computers, but have backups stored in a secure and dry place that will be safe even if you flood or have a fire.