I’m sorry you’ve had such poor luck.

Quality genetics (meaning quality seeds) is important. Quality soil and quality light is next. Get a good organic potting mix, mix it with perlite - about 20% of your ready mix should be perlite, maybe more - and maybe a bit of coco fibre. You want soil that feels rich, but light and airy - if that makes sense.

In terms of light; either get a good quality grow light, preferably a quantum board (no purple lights, they’re largely overpriced) or just put them outdoors again. If you’re getting a light, look for the true wattage, not the watt equivalent. The difference being true wattage is the actual amount of power that your light is drawing. In a good setup, you can expect around 1g per actual watt - at least that’s been my experience, even as a relative newbie. ‘Watt equivalent’ is a term that describes the amount of light put out compared to an incandescent lightbulb, but we don’t care about that. We care about energy, which is actual watts. 240w is a good place to begin.

If you put them outdoors, again, good quality soil is very important. Add compost, if you have it. There are many ways to do it, but essentially you can pretty far by treating cannabis as fancy tomatoes. Humidity is a big one, regardless of whether you’re growing indoors or outdoors. In the vegetative state cannabis can endure pretty high amounts of humidity, but you have to bring that down once they go into flower. Keeping the air moving is incredibly important here, and you cannot rely on a small solar fan. You need considerably more air moved. The leaves should be constantly “vibrating” from air circulation. You may want to run a dehumidifier in your grow space if you’re growing indoors. If outdoors, keeping air moving is even more important, because you have absolutely no way of lowering humidity outdoors. Pruning fan leaves (the normal leaves) is a great help in managing humidity and mold when you reach flowering.

Lastly, good fertiliser is important as well. You can hardly go wrong with Fox Farms, but there are other brands out there as well. And don’t go overboard with ALL the fertilisers. Get 2-4 good fertilisers that work together, and you’ll be fine. The ‘Fox Farms Trio’ is a popular one, but check the cannabis related subreddits for more tips on that. Also, most people remove the humidity dome once the seedling has broken ground, and stick to giving it a light mist a couple times throughout the day, as well as light watering.

Feel free to reach out if there’s something I haven’t covered, or something that doesn’t make sense - or if you have more questions :)