The basic idea is that players should get rewards for bringing new players to the game.

There should be an input for a "referrer's name" where my friends put my username if I tell them to play Toribash. If one of my friends plays 100 matches, buys items from the Torishop, wins auto-tourneys, etc... , I should get some type of reward (TC, forum gear, exclusive items) for bringing an active player to the game.

There would be different tiers of rewards such as

100 games played - referrer gets 10 TC
1000 games played - referrer gets 100 TC
1,000,000 TC spent - referrer gets animated avatar on forums

(These are just examples for you to understand the idea).

Especially with Toribash Next coming out sometime in the future, which will hopefully bring a large influx of new players to the game, It would be great to have a referral system in place.