If your using a decent premix soil, not stuff from the back yard, then you shouldn't need any nutes for veg if your just going 3 - 4 weeks. I would recommend a 1 part bloom fert. I use age old bloom, and my afgooney loves it. My best advice is to stay very simple with soil, your not missing anything not buying $200 worth of nutes. If you want to get into lots of additives and micro management of doasges do it in hydro.