That's not exactly helping, mate...
Which era ? which cars to put on ?
Anyway... I've already filtered my CM, so lets see what's worth it in my opinion :
Vintage racing : All of Fat-Alfie's tracks, period. Also, Donington '38 by Jim Lloyd, All Sergio Loro's tracks but as they are not all free, focus on Sandevoerde, Rouen, Stardust and Djursland for the "not free". Bryar by Gary_Lapidus, very recent one, and worth it. Zolder 67 updated by Teddie, Gnoo Blas by Mike Cantwell, Kyalami '67 from RT, Lake Garnett by Thrashy, Le Mans 67 by Terra21, Longford updated, Monaco 66 by RT, Montjuic 75 from Rainmaker, Napoli from Italotracks, Nemuno Ziedas, Preluk 74, Riverside, spa 66 and pre-war, Nurburgring 67, Tocancipa and San carlos from Elias Viejo, Willow springs by Esprit3905 (but others versions are worth it too)... And I probably forgot some.
Modern racing : all of reboot Team (RT), period. also, all of Lilski and Doublezero. Also, Bikernieki, Charlotte, Chang, Croft, Oulton park, Fort Grozniy, Horsma raceway, Interlagos (by VheEth), Kyalami, Le mans, Lucca Ring, Mills metropark, Moscow Raceway by SMP, Okayama by Mitja Bonca, Oschersleben by TM-modding, Ottawa by Thrashy, Pinwheel by John Harding, Road Atlanta by JohnR, Sachsenring from Gunnar333, Shanghai Tianma, Sidi Daoui from JLCJB, Smolensk ring, Neva ring, Sveg by Leon Sutfeld, Tianjin autoworld, Tobeka, Tor Poznan, Tsukuba (I recommend Esprit3905 version, and basically all his conversions too), Virginia, and most of Chiquifreaky conversions. Aaaand I probably forgot A LOT.
There. That's a start. And don't ask for the cars now, or it's gonna take all night.