Selling your textures is the easiest and fastest way.
The more badass texture, the badasser the price.

I would say betting, torneys, duels, art and boosters.

I dont get the way duels work can anybody explain?

Loser pays his TC to winner. As simple as this.

Duels are risky though. I would say bets.

Dueling is the fastest and the riskiest way to earn TC. Marketing requires effort for it to shine.

When you have very low TC, win some tourneys until you have around 5k. Now, start dueling if you are confident you can win. Your goal for starting marketing is 20k because a good percentage of items are available to be bought in the range of 20k. Marketing is much less riskier than dueling, but it is your call to choose which. If you play your cards right, you can walk out rich by both dueling and marketing.

lol JSnuffMARS is in my clan
-----

What are boosters and how do you make them. Also how do you set up deuls.

The easyest way is to buy a booster and play hard shovel core in quick aikido or jousting servers, this will bring you tons of tc, incase of wins.

All that you need is around 50 USD and 2 hours / day for hardcore game and you could got ... 25k - 100k /day.

To set up a duel, make sure you are operator in a server. then do the command /duel <amount>. from here, it will take everyone to spectators. then do /en, or /enter to enter the game. when the match starts, it will take that amount of tc out of your account. if you win, you get all the earnings. If you lose, you lose that much tc.

Like evreyone else said deppends on what you are good at.
Tourneys for me.