Before S06 E03, with all the hints so far (based on what we know and what we don't know about the suspects). Chances (approximately) of each suspect to be Red John are:

24% - Gale Bertram
23% - Ray Haffner
17% - Thomas McAllister
15% - Someone Else
11% - Reede Smith
5% - Bret Stiles
4% - Bob Kirkland
1% - Brett Partridge
0% - Patrick Jane