Because of energy/volume inefficiencies don't try to stack ram pumps, just run it as a single stage.
The formula of interest can be found at
Mother Earth News:
D = [(S X F)/L] X 2/3
where,
D is the amount of water delivered in gallons per minute (gpm). S is the amount of water supplied to the machine in gallons per minute. F is the fall or vertical distance in height between the supply of water and the ram. L is the lift or vertical distance the water is lifted from the pump to the storage tank. The fraction of 2/3 represents the efficiency of the
ram.
Plugging your numbers into the equation...
Let's say you are after 24 gallons per day to make the math simple. That is 1/60th gallon per minute or two ounces per minute... Out in the desert I would be thrilled with that much water!!!
1/60 gallon = [(S * F)/L] * 2/3
==> (L * 3)/(60 *F *2)= S = (100 *3)/(60 * 3 *2) = 0.8 gallons per minute of flow through the ram to get 2 ounces per minute out the top.
So, if you sized your feed pipe to supply 8 gallons per minute, then you could expect 20 ounces per minute out the top, or 240 gallons per day.
It seems to me without actually running any math or building any devices, that a water wheel driving a piston pump would be easier to implement, more reliable, and would supply more water to the top of the hill.