I would not say that I have a green thumb. Now and then, I buy a pot of Basil in the hope in keeps me company. But the best I can manage is big leaves turning into small leaves turning into empty stalks. In other words: a slow death for the poor thing.
Sunlight may be the least problem - maybe to much even? Regular watering surly is. Variable conditons. That sounds like a software problem. You really want a neutral container to build software in, because that way you eliminate side effects. The gardening equivalent would be a literal container. Light can be supplied at all hours, moisture stays inside and the temperature is stable.
Turns out, that is called a Space Bucket.
I begun with some bell pepper seeds (as they come complimentary with the ingredients for salad). Paper towles, water, cling film on top. The seeds sprouted in a few days and I transferred them into a big pot.
As the shoots did not grow, I repurposed a LED strip. It's good for outdoor use, so I figured a little spray wouldn't hurt. Now the light still escaped mostly plus I can't sleep with a brightly glowing pot in the room. So the next step was to add some kind of top.
Molding some aluminium foil with a big bowl is fast and easy. A rim of duct tape almost perfectly seals light and moisture in.
And guess what? After two days (and nights!) of constant light, the shoots begin to grow their first set of real leaves! The LED strip is slightly warmer than room temperature and keeps the plants cosy. I still have to lift the top once a day to supply fresh air - but I wanna have a look anyway.
It's not a Space Bucket yet, but I'm half way there.