I believe, this list is based on Test only.
I'll rank my list in two way - 1. type of bowlers & 2. Over-all. And, I am leaving spinners from the era before first world war. There had been some of the best spinners in ancient days like Briggs, Blythe, Peel, Peate, Ranji Horden, Palmer, Trumble, Rhodes..... it's not possible to consider them just based on stats.
By Type:
Leg (Wrist) - spinner (Including Left-armers)
1. Warne
2. Bill O'Reilly
3. Benaud
4. A Qadir
5. Grimmett
6. Kumble
7. Chandra
8. Gupte
9. McGill
10. Yasir
SLAO
1. Bedi
2. Verity
3. Herath
4. Underwood
5. Qasim
6. Jadeja
7. Lock
8. Wardle (Bowled Chinaman as well)
9. Valentine
10. Shakib
Off-spinner
1. Murali
2. Laker
3. Saqlaine
4. Prassanna
5. Lyon
6. Tayfield
7. Swan
8. Harbhajan
9. Ashwin
10. Ajmal (Should have been higher, .....)
Now comes the tougher part. Instead of ranking over-all position (which is impossible for me), I'll do it in an innovative way - I'll pick 6 Bowling combinations with a Leggi, Offie & SLAO spinner, to my best knowledge on combination. It's not like the three of the first team are the best three, rather I have picked bowlers who can complement each other most - sort of my dream attack. And, I haven't considered the batting ability of the bowlers at all. List is ranked based on overall strength (A is strongest, F is weakest)
Team A: Warne, Saqlaine, Verity
Team B: Murali, O'Reilly, ** Bedi
Team C: Laker, Benaud, Herath
Team D: Grimmett, Prassanna, Qasim
Team E: Qadir, Tayfield, Underwood
Team F: Chandra, Ajmal, Jadeja