How can I create a clan? Does it cost TC or QI? Where can I create it?

Everything is in here and here...

Wrong >:c
It is free but if you want the tags to appear ingame or your clan name appear forum you need to have Toriclan.
Monthly Toriclan costs 10k TC and u need to pay it every month....
Official Toriclan costs 50k, and it will be decided whether the clan can go or not.
The tag of the clan will have a - sign before the clan tag if you use the monthly Toriclan.

You simply make a thread in the clan discussion with your clan's tag and/or name.
Example:
[Combo] discussion thread
and if you don't want too much of a mess especially for people wanting to join, make a thread in the app center.
Example:
[Combo] recruitment thread

If you feel like it, you can pay 10k TC for your clan to become unofficial and when you think it's ready, 50k to apply for official and your clan's very own Forum board.
however, not all clans are accepted.

I do not recommend making a clan right now because you need friends to start with. Also, you should get more experience around forum.

^
That.
Making a clan requires forum and game experience, plus, of course, friends. If possible, responsible friends. And if you want some nice piece of advice, don't create a clan just for fun or because it looks cool, because if you don't get your mind into it, like seriously, it will most likely fail, in which case you'd be better off joining an already existing clan.

But, talking about the requirements, Eason's links are right. Read their content and you'll know what you need.

There are two types of clans now. There are unofficial clans, and then there are the officials. The key elements, however, is everything Wolf had said in the post above.
You can make an unofficial clan by following this, and sending the required proceeds to Fish. To make an official toriclan, read this. You may send the funds to either Fish, Uric, Brey, Lightningkid, Hamr or Delaid.