A 250GB external hard drive is a moderate expansion of your space needs. A good amount of space if you feel the need to transfer some files into it that aren't in regular use but still are wanted. Good as extra space to work out of as well, in case you want it separate from your general work. There are a few different options such as shockproof or if it is a Solid State Drive or the older HDD.
A basic expansion
250GB is a moderate amount of space given how much information one can gather on just their phone over the course of a year. An external hard drive is a very useful device for storage and even everyday usage depending on the kind of work you are usually doing. Hard drives are quite compact and easy to carry around. Sometimes there are old files that are not really needed and are just taking up space such files can be moved into a hard drive to empty to some space out. Even in case your laptop crashes you have the hard drive with your files safe.
The different types
Hard drives are available with rugged shockproof cases so they are even safer in case it takes a fall. Another thing to see is what kind of hard drive you want between the Solid State Drive (SSD) or a regular HDD. The SSD is faster as it has no moving parts and uses electric circuits to write and retrieve information, this is based on the Flash Memory technology that powers our RAM chips as well. The wear and tear between the SSD and HDD varies with the HDD drive taking more hits over time due to its moving parts.
A drives space that you choose is based on what kind of files you are working with or need to store, if it is things like lots of high-quality music files or video files then a larger drive is recommended as a 250GB external hard drive would fill up relatively quick.
Connectivity and the known brands
All external hard drives connect to a computer through either USB, FireWire, eSATA or WiFi. Some require external power but a 250GB one wouldn't need that much power unless it was using WiFi to connect. Known and market-tested brands that make External Hard Drives are Western Digital, CalDigit, Seagate, LaCie, ADATA and Samsung among others.