How about just reading about article I provided and clikcing on the top GMs listed?
http://sabr.org/latest/armour-and-levitt-best-25-gms-baseball-history
Branch Rickey? He's the consensus best of all-time, at least before Theo's Cub championship. He nearly did it twice.
The Cardinals had last won a WS in 1886. They hadn't made the WS in 36 years. They moved Rickey into the GM role in 1925 after a 65-89 record in 1924. Here's how quick he built a winner:
1925: 77-76
1926: 89-65 WS Champions.
They made the WS in 4 of the next 8 years (winning 2). From 1926 to 1946 the Cardinals won nine pennants and six World Series.
He then took over the Dodgers, and although they had just won 104 games, the war devastated a roster full of mostly over-aged players.
1943: 81-72
1944: 63-91
1945: 87-67
1946: 90-60(signed Jackie Robinson before season)
1947: 94-60 Lost WS
He was squeezed out of the GM job soon afterwards, but the Dodgers went on to win with the team he built.
He then went to Pitt and built a team by acquiring Roberto Clemente (another first) and many others. He left the team, but the won a ring 5 years later.
He joined the Cards again as a senior adviser in 1962 after an 80-74 season. Then...
1962: 84-78
1963: 93-69
1964: 93-69 Won WS
(He was not technically the GM though.) The team went on to win in 1967 after he left.
#2 on their list is Pat Gillick. He first built an expansion team itno a team that won 86 or more games for 11 straight seasons- finally winning a ring in 1992 (after 16 years).He was not there for the ring.
He then joined Baltimore, where they won the ALCS twice- their only two playoff appearances in 20 years.
In Seattle, he traded away and lost to free agency their two best players, but the team won over 90 games all 4 years he was there.
Finally, he took over the Phillies and in 3 years they won a ring...their first in 28 years!
Then, there's ED Barrow at #3.
He took over a team (the Yankees) who had never even won a pennant. By 1921, they won their first. The Yanks won 13 more pennants and 10 WS under his leadership.
Let's look at #4 Bob Howsam. He was put in charge of the Cards and after the 1965 club fell to seventh place, Howsam traded three aging regulars — Bill White, Dick Groat, and Ken Boyer — very popular players who Howsam correctly believed were near the end of the road. In early 1966 he acquired Orlando Cepeda from the Giants, and after the season picked up Roger Maris from the Yankees. Maris and Cepeda became the number three and four hitters for the club that won the next two pennants and the 1967 World Series.
But by that time, Howsam had moved on to Cincinnati. In 1971 a number of Reds had off-years, and the team fell to 79-83 and a tie for fourth. Howsam and Anderson determined that they needed more team speed to return to the top. In December 1971, Howsam pulled off his most famous deal, trading Lee May, second baseman Tommy Helms, and utilityman Jimmie Stewart to the Astros for second baseman Joe Morgan, infielder Denis Menke, outfielders Cesar Geronimo and Ed Armbrister, and pitcher Jack Billingham. Billingham and Geronimo were key members of the upcoming teams, while Morgan, an unappreciated star in Houston, became the best player in baseball. Howsam also added outfielder George Foster and pitcher Tom Hall through trades in 1971.
It was the Morgan trade that turned the Reds from a good team to one of the best teams ever. Over the next five years (1972-76) the Reds won 502 games, four division titles and two World Series.
#6 John Schuerholz.
The KC Royals were under .500 in 1981. The team won it's first WS ever in 1985 ...in just 5 years being there.
He joined the Atlanta Braves after the 1990 last place season (65-97).
His first year, he got them to the WS! (94-68)
The next year, 98-64, the lost the WS again. They went 104-58 in 1993, but lost in the NLCS. After an off year in 1994, they won the WS in his 5th year in 1995. Although they never won a ring again, they won their division 10 straight years after their WS win.
#8 Harry Dalton
He took over a very good Orioles team, but he then traded for Frank Robinson who went on to win a triple crown. They won in his first year (1966). The Orioles fell back in 1967, largely due to injuries to Robinson, Jim Palmer and Dave McNally. When the club failed to rebound adequately in 1968, reaching the All-Star break at 43-37, Dalton fired manager Hank Bauer and gave the job to Earl Weaver, who had spent many years in the organization as a Minor League manager. Weaver was not shy about making changes, playing Don Buford (a great Dalton acquisition) and Ellie Hendricks, and taught the Oriole Way that Dalton had long championed in the minors.
After the 1968 season Dalton traded outfielder Curt Blefary to Houston for pitcher Mike Cuellar, who won 125 games over the next six seasons. The next three years the Orioles won over 100 games, waltzed to division titles, and swept the ALCS. That they only were able to win one World Series masked how great this team was. So good, in fact, that Dalton only had to make one trade of note — he dealt some unneeded players to the Padres for Pat Dobson, who won 20 games in 1971. In six years Dalton won four pennants and two World Series in Baltimore.
He then went to the Angels and made some big moves to turn that team around, but they never won a ring. He then went to Milwaukee, where the team had never had a winning season. They were 67-95 the year before he took over, then they went...
93-69
95-66
86-76
62-47 (lost DS)
95-67 Won WS in 5th year
You see, it's happened before... many times.