Wordpress blogs are based on two types :-
1. Hosted by Wordpress.com
Hosted by Wordpress :- These blogs don't cost you any money and only usable if you want to get space on internet to deliver your views. You get many limitation in Wordpress.com, you can't add plugins, themes, 3rd party ads, etc. You only have option of in-built functions provided by Wordpress to you. This type of blog costs you Rs. 0 whereas you have option of buying a custom domain and redirecting it your blog. This will cost your about 10$ per-year.
Self-Hosted :- Wordpress is the world's most used CMS system. Wordpress.org (based on self-hosted wordpress) comes with no-limitation. You get access to all types of plugins, themes, etc. Apart from that you can code your own theme and use it on this. Usually to get wordpress.org blogs you will need to get a hosing which will cost your about 100$ per year (minimal cost of good hosting) and getting a domain will cost your around 10$ per year. This is the best CMS system if you are serious about your blogging career and seriously want to earn from it.
If you are opting for Wordpress.com for practice purpose, then I would suggest you to go for Blogger. It is a Google's product with same specification as Wordpress.com but it comes with minimal limitation and better support from Google as well.
I am currently pursuing High School and planning to pursue career in Computer. Currently, I work on one of my blog - JTech Articles.