Since you mention a server, you'll probably want to run the daemon,
The size of the blockchain has eclipsed 20 GiB a long time ago, so you'll want to run with the flag
-prune=<n> which gives a limit for the storage used for the blockchain data. The blockchain data will still be downloaded and verified, but old parts will be discarded once the limit is reached.
n is given in MiB. There are some other data requirements, so you should leave some space, e.g.
-prune=5000 would leave you with approximately the last five weeks of blockchain data. If you want to access all transaction data, you would need to invest in more hard disk space to be able to run without pruning.
Unless you want to actively use it for transacting, you should run it with
-disablewallet to save some resources.