Could really do with any help towards nutrient choice

growing a variety of autoflowering strains on my first grow, just wondered if anyone could recommend specific products with proven results that wont break the bank, also a simple explanation as to why nutrients are required and which are essential at what stage would be very much appreciated, how many bottles do i need? etc. i dont want to buy random bottles that may conflict or not compliment each other
thanks alot guys !!

Soil or hydro?

Using soil ! help appreciated

I use Alaska nutes in soil with great success. Check out amazon for em.

I've been testing the Xnutrients line. (Grow, Bloom, and Micros)
I haven't fully completed a run with them yet but so far I'm liking them. (and I'm REAL picky)
Low cost and high quality, with excellent customer service too.