How to make a rating based on the results of fights?

Question

Algorithms

There are match results. Victory/Loss. How to make a rating and divide by Tire?
There is an Ello system, but for it you need to already know the ratings. How to start?

Answer 1

You assign a starting Elo to everyone, for example, 1200 (as chess.com does).
Next, you start calculating the rating of players, choosing games in chronological order.