The best torrents to build a good ratio are:

1- Formula1 (F1) "The best".
2- NBA
3- Football (Soccer ) Like EPL, Bundesliga, UCL.

you should be one of the first Leechers and don't grab big size torrents until you build a good ratio over 1.5.
and remember 100% FreeLeech Torrents are rare on the Tracker.