This will help you if you grow in soil:
https://www.growweedeasy.com/soil
And you're definitely going to have to transplant into bigger pots or you'll have root problems and the plants won't grow.
https://www.growweedeasy.com/choose-right-pot
I like to keep it real: growing cannabis is easy IF you know what is necessary to get the results you're looking for. Some folks will end up with small, lanky plants with very small buds because they don't know what they're doing; the bud won't be very potent and there won't be much of it. I don't really think it's easy to just jump in and grow top shelf bud, right off the bat, without reading and learning a lot or having someone who teaches you. In my opinion, it's a waste of money if you don't know about soil, nutes, lights, temps, humidity, pH equipment to keep your eye on the pH level, etc. etc. There are a lot of things that are fundamentally important to know IF you want to grow some phat buds.
I grow hydroponically, and I started in July 2016; I've learned a lot of lessons from the mistakes I made on each grow, as well as learning from what I did right. I found the companion website to this forum--
https://www.growweedeasy.com and started reading everything I could about hydroponic growing. I got lots of help on this forum, but I had to acquire the knowledge to prevent problems from happening and to keep my plants healthy. And I'm not even three years into this, so I'm still learning a lot!
I recommend that you post pictures of your set up and get your hands on some nutes on Amazon.com real fast if you don't live where you can buy it easily. As seedlings grow, they will get hungry; if you want them to thrive and grow fast n strong, give them the right nutes. Nutrients range in prices; I think a lot of folks use General Hydroponics nutes, which I believe are also made for soil. I use Future Harvest nutrients.
With time, you will begin to fine tune your grow environment to harvest the best bud you can. I had to invest in all kinds of machines and gadgets to tune my grow room so that the hot, muggy place I live wouldn't do damage to my plants. And I learned fast from a horrible case of root rot because my grow room was too hot and my reservoir water was too warm. I had to invest in reservoir chillers and a large dehumidifier, among many other things. Your situation will be different with soil, but some things are the same no matter how you grow.
We are definitely here to help, but gwe will give you the basic knowledge of soil growing much faster. At this point, growing Cannabis is one of the greatest pleasures in my life, and I just want to keep getting better at it. Any more questions, just ask!! ;-}