Dont fertilize for the first 3-4 weeks of growth. Then get a complete, soluble fertilizer such as Peter's, Miracle Gro or Schultz's with the lowest analysis available (NPK). Use less than the recommended amounts printed on the label such as a 1/8th to 1/4 solution to help prevent over fertilization (the most common beginner mistake) and only fertilize every 7-10 days, slowly ramping up the concentration as the plant matures. If you are determined to stay "organic" , a basic 5-1-1 fish emulsion can be suitable for your entire grow. Invest in a digital pH meter and small containers of pH "up" and pH "down". Mix the fert solution you chose then slowly adjust the pH to a range of approximately 6.1 to 6.7 so that macro/micronutrients will be available to the plant and not tied up due to acidity/alkalinity issues. Don't think that you must buy the fanciest , most expensive fertilizers for good results. Many times you are paying for colorful, trippy graphics on the labels and little else. Invest in good genetics from the start and the plants will need little besides water, light and rudimentary care from you.
