You get free Toricredits by playing online, at Official servers: 10 TC each win.
You can also make textures, if you are good with art, or buy/sell items, marketing, etc.
Theres many ways to get Toricredits.
You can win tourneys in-game, or automatic tourneys, 500 TC each tournament win.
Gamekeeper's Tourneys are usually 7000 for first and 3000 for second. Prizes can be items too.
And thats it, hope it helps.