yes, amazon and ebay and often online hydro has same price on lights. Yes, skip the nutes if growing in soil that already has nutes in it until you see how it goes. After that it is a balance between giving them what they need without building up salts in the soil. That is another myth I bought into that autos don't like to be transplanted. Starting in small containers and transplanting at 30 days gives me an extra 30 days of salt free medium for flowering and I can gunk up my seedling mix all I want, not that they need any gunking. But yes, the alternate one water/one feed is a method of postponing salt build up. Many ways, fit it around your personality and what has worked in the past. Good time of year to move inside.
Yeah they sell them on amazon I add nutes on every watering. Its best not to give them too much one time and then not enough the next time in order for it to average out in the right area. It's best to give them the correct dosage every time and keep it consistent. Alternating between under-dosing and over-dosing is a very old way of doing it and most people now do it the more modern way You can't go by an amount of days because the size of the pot and speed of growth will have a huge impact on when to start adding nutes. You want to add them once the soil starts to run low on nutrients, and I find this usually happens not long after the tips of the leaves reach out past the rim of the pot