the best bookmaker I can suggest is for sure betfair.
Because you can find best odds, because you can trade the odds making back & lay, because matches are and remain always open.
I built my model with patience
trying to figure out what kind of info where important to me to know, to build a rating about two players.
I decide to keep track of wins, surface, player's shape, skills. I combined all in a (small secret) function in order to obtain the rating I publish.