Well, I only have experience with the
General Hydroponics Flora Series but find them to be quite good. They are a 3 part liquid that you need all 3 parts to make work. Just not the cheapest on the market.
You will want to make sure that you get a pH testing kit, some pH up and pH down. Test the pH of your
nutrient solution daily and adjust if needed. If the pH level is to high or low for the plants you are growing, your plants can starve even with the best
nutrients. Fortunately you can get a pH testing kit for about $8 and the "pH up" and "pH down" is not expensive either, but it's important to check it daily.