there really no "exact" ratio. But the common one for 2L bottle is 1.5-2cups sugar, 5-6cups lukewarm water, 1/8-1/4 teaspoon of yeast. (baking soda optional)
The only thing that may change with more or less sugar/water/yeast is the time that the mix lasts.
Also make sure that there are no leaks and that the mix is at warm room temperature or atleast in a water bucket with a heater.
Another thing that may affect the co2 getting to the tank is the length of the airline tubing. The shorter the tubing the better it is.
I used half tsp yeast, 2 cups sugar, and filled the bottle to the shoulder. I had a leak but it was where the tube goes into the bottle but i soon fixed that.
Now i use this because it produces way more co2 and lasts longer:
1 and a half tsp baking powder, three quaters tsp yeast and water the same.
The higher the specific gravity of the water, the higher the osmotic pressure on the yeast cells. You need more water.
My recipe is 2.5cups sugar, 1/4 - 1/2 tsp. yeast, 1/2 tsp baking soda, and a 3L bottle filled ot the shoulders. I activate the yeast in hot water from teh tap and a wire wisk...the wisking is to incorporate oxygen to jump start the yeast before pouringit in the liquid.
1 3L bottle in the 20g and 2 3L bottles in the 75g is enough to keep a 4dkH drop checker in the green for about 3 weeks, using a hagen ladder for diffusion of CO2.
Bread yeast is relatively hearty. Depending on the age of your yeast fermentation may start quickly or up to a day or so after pitching. If things aren't happening after that, pitch more yeast.
The higher the concentration of sugar (specific gravity) of the wort, the longer it typically will take for your yeast to start. Not a big deal when your making 5ga of beer or wine.
Like everything else you'll need to play with your mix until you hit the mixture that gives you a good long fermentation.