From Tokyo to Takasaki:
The Joetsu/Nagano Shinkansen requires about 50-60 minutes to reach Takasaki from Tokyo Station. The one way fare is 4290 Yen by non-reserved seats.
By local trains on the Takasaki Line from central Tokyo, the one way journey to Takasaki takes about 110 minutes and costs 1890 Yen. There are several direct trains per hour from Ueno Station, and at least one direct train per hour from Shinjuku Station (running on the Shonan Shinjuku Line).
From Takasaki Station to the Daruma Temple:
Infrequently departing "Gururin" loop buses connect Takasaki Station with Shorinzan Temple. Take the Shorinzan Line Number 1 and get off at "Shorinzan Guchi" bus stop. The one way trip takes about 25 minutes and costs 200 Yen. To return to Takasaki Station, take the Shorinzan Line Number 2, which runs in the opposite direction of line number 1.
Alternatively, the temple can be accessed in a 15-20 minute walk from Gunma-Yawata Station, two stations, 5 minutes and 190 Yen northwest of Takasaki Station on the JR Shinetsu Line. There are one to two trains per hour.
Finally, by taxi it takes about 15 minutes and 2000 Yen to get from Takasaki Station to the daruma temple.