You could plant in a 1.7 gallon container from the gate but it is really difficult especially when new to manage watering, gnats, stem rot and etc. Also it is easier to manage low dose ferts in a small cup, which you will use at first. Most growers I've seen online and everyone I know use those red plastic solo cups you can get from the grocery store with holes cut in the bottom. To make the holes poke a little hole and scissor them out if you aren't great with an exacto knife.
All strains grow at a different rate we categorize them into groups fast/slow and easy/hard to grow. But it isn't hard to manage this you simple thoroughly water the plant then wait for the planter to be virtually dry. You can tell it is dry because when you pick up the cup it is almost as light as it was when you first put just the dry dirt into the cup. When you are watering every 1 or 2 days the roots are taking up almost the entire planter so it is time to transplant. No nutrients for the first 3 weeks is a solid rule, very few strains will need nutrients before then and most will be damaged instantly by Nitrogen if the rule is broken.
I wasn't speaking about organic soil water only growing at all that is a different animal. If you are actually doing that when you first started I would be surprised, I assume you are going to be giving fertilizer in some form. If you need help with that mention so. If you were growing truly organic you would have composted specific ingredients to grow cannabis, or bought it from a provider such as kind soil.
