How necessary is buying a domain when I'm just a graduated student? I'm a graduated student and about to make a poster for my institution's conference. I would like to have a website so that I can have more space to present in the poster while still have a data to show if necessary. If I choose to have a free domain, I will have an URL contain the host name, e.g. myname.wordpress.com. If I buy a domain and use free host like Wordpress, I can quickly build my website up but the price is not cheap. If I buy a domain and a host, the price may cheaper but I have to build it by myself. I want my website to look professional (and impressive) on the poster so that using a free domain may not a good choice, but I also consider in the economic prospect. In my country, $10 is not a big deal, but also not a thing that people is willing to spent easily.
If your department/school won't give you support... 

The domain should cost you between $0.50 to $0.99 USD for the first year. Hosting costs range a lot, but many offer deals for the first year that cost about $12 USD.

After you have your own server and domain, it is trivial to setup WordPress on your own server. 

Thus you get the best of both worlds, extremely affordable and easy! Besides, I recommend most people have their own personal website for their portfolio and such anyway.