I’ve kept mine in relatively dark corners for years and they’ve always done well enough. For the best growth, place your Ficus ‘Alii’ next to a window that doesn’t receive direct sun (like a north-facing one).
As with most tropical plants, room temperature is actually perfect for your Ficus ‘Alii’. If you feel comfortable in your home, then you can safely assume your plant does as well.
The best way to figure out whether your plant is thirsty is to just stick a finger in the soil. If it feels dry, you can give your plant a drink. If it still feels damp, it’s best to check again tomorrow.
A normal, high-quality houseplant soil works absolutely fine, although I do recommend also mixing in a handful of perlite or fine orchid bark for added drainage.
If you feel like the soil tends to dry too quickly, you can consider adding some peat moss or coco coir to the mixture. And if you’ve got some compost or worm castings on hand, that’ll definitely help, though it’s by no means a must.