“(When you) Get a hunch, bet a bunch” has been a gambling saying since at least 1937. The saying was also adopted by the racetrack, with this ending: “Get a hunch and bet a bunch—and all next week you’ll eat no lunch.”
 
“Get a hunch, bet a bunch” applied to picking investments by at least the 2000s.
   
         
Google News Archive
29 May 1937, Owosso (MI) Argus-Press, “Hollywood’s Bob Rossen: Greatest Hazard in Creative Work Is Success, He Says” by Hal Boyle, pg. 9, col. 5:
NEW YORK (AP)—“The greatest hazard in creative work is success,” said Robert Rossen, one of Hollywood’s few top triple threat men.
 
“Once a man wins success he wants to hold on to it too mcuh. He becomes afraid to take chances and do risky things. He becomes cautious and repetitious.
 
“I believe there’s a lot of sense in the old dice table saying; ‘get a hunch — bet a bunch.’”
   
17 August 1941, New Orleans (LA) Times-Picayune, “Rambling Gambler Finds a Poet of the Dice Tables; Croupier Makes Jingles While Raking Dough of Customers” by Theman Whowentogamble, pg. 15:
“All right folks,” he (a croupier—ed.) barks out of a corner of his mouth, “get a hunch and bet a bunch.”
 
Google Books
The man with the golden arm: a novel
By Nelson Algren
Garden City, NY: Doubleday
1949
Pg. 11:
... Little Joe or Phoebe, Big Dick or Eighter from Decatur, double trey the hard way and dice be nice— when you get a hunch bet a bunch— bet a dollar and then holler—make me five to keep me alive—it don’t mean a thing if it don’t cross that string—tell ‘em where you got it and how easy it was.
 
Google Books
Kentucky Derby Stories
By Jim Bolus
Gretna, LA: Pelican Pub. Co.
1998
Pg. 29:
HUNCHES. Racetrackers like to say, “Get a hunch and bet a bunch.” They never add the next line, which is “and all next week you’ll eat no lunch.”
 
Google Books
Modeling financial markets:
Using Visual Basic.NET and databases to create pricing, trading, and risk management models
By Benjamin Van Vliet and Robert Hendry
New York, NY: McGraw-Hill
2004
Pg. 16:
There is an old saying in the trading business, “Got a hunch, bet a bunch.” As with most old sayings, this one is based more on fact than fiction. In most human endeavors it is more fun to do than to plan. This trait is very human and is only driven out of people by years of schooling and life.

Google Books
Options and options trading:
A simplified course that takes you from coin tosses to Black-Scholes
By Robert W Ward
New York, NY: McGraw-Hill
2004
Pg. 286:
Proprietary speculation is the catch-all phrase we use for any trade we haven’t been able to categorize separately, any outright price bets on assets where the trading desk or management “has a hunch and wants to bet a bunch,” and any arbitrages that aren’t really arbitrages but are in the portfolio, onetheless, and stay long after the bloom is off the rose.
     
Barron’s
MONDAY, JANUARY 25, 2010
HOT RESEARCH
Goldman Sachs’ 2010 Rebound
(...)
Bank principal risk-taking for clients is unlikely to go away. There is a fine line between proprietary investing (i.e., “got a hunch, bet a bunch”) and client-supporting capital commitments (e.g., listed equity block trading).