First off what kind of soil are you using?
I'm guessing Miracle Grow so you don't want to add any nutes for AT LEAST a month; if you do you might burn your plants, or you might not. You could flush the soil but it's not needed. I grew my first in MG and it's doing awesome.
Technically you don't need to use ANY nutes but nutes will make your plant grow more and bud bigger. As long as you don't give them too much.
To keep it simple you should start by using an all in one for veg and one for flowering. I use
Bontanicare's Pure Blend Bloom and Flower.
When you get into flowering you can use a bud booster like Monster Bloom or a whole regime like Open Sesame, Beastie Budz, and Cha Ching. Make sure you ONLY USE THEM AS INSTRUCTED OR YOU WILL BURN THE SHIT OUT OF YOUR PLANTS!
Some strains like more ferts and some like little to none. For normal bag seeds try this:
After 2 weeks veg start with 1/4 of what the manufacturer says to use and feed with every watering. Some feed with 1/2 nutes every other watering but 1/4 will give you more even feedings. If your plants respond favorably then after about 2 weeks start with 1/2 nutes every time or full nutes every other time. If your plants react badly then dial it back to 1/4 nutes.
Now the real art comes in telling what is nute burn, what is nutrient deprivation, and so on. You can be told a million times but until you experiance those yourself you probably won't "get it."