Drogrowno,1 gallon pots are good enough to complete the etire growth.But yes,I advise that you transplant to 3 gallon pots,or 2 gallon atleast.Remember,some people actually grow and succesfully flower in small soda bottles,so yes,1 gallon is enough..however,the more rootspace/root mass..the bigger,faster the plant will grow.Remember that most plants usually double if not triple in size during flowering...so you should transplant.If you can find Superthrive,buy it.Its mostly B-1 vitamins which help releive stress due to transplanting.
Mollases is extremely good for flowering plants...it add size,mass,resin,taste,and overall vitality to the plants....it is 1 tablespoon per gallon of water..try to preheat the water,so the mollases dissolves better....also,it is recommened to flush the plant with mollases/water.Any more questions,just ask!