What is the breakdown of how many Legend Tokens you get?

Do you get any for just playing a game?

Not necessarily every game.

If you are Champion do you get more?

No.

You obtain legend tokens by leveling up. You receive 600 legend tokens every experience level, so you should have 12000 of them (enough for a legend) by level 21 (every 20 level ups).

You can also use the legend tokens for different cosmetics in the shop.