I have 18 plants. The first few I got were succulents and cacti and I read that you should water them thoroughly and allow the soil to dry out completely - at least a week or two (the longer the better actually, but not more than a month) - before giving them a thorough water again.
I usually just water the soil till the water just stops 'sinking in' if YKWIM. Don't want to drown it. Then I leave it to dry. Succs like a lo-o-t of light too so if you put them on windowsills they just sit there happily. They are unhappy if you put them in the middle of a room that's further away from a window.
Other plants have different rules but in my experience I actually treat them the same way I do the succs - water and then leave! Usually once a week or so - but if the soil still appears damp don't add any more water, leave it till it looks dry and then water. Seems to work for most plants (IME).
With non-succs you have to mist them every day because they like humidity. I have to do that with my Dragon tree, my braided money tree and my Devil's Ivy.
And read up in where you place them - succulents/cacti thrive in a sunny south-facing window. Other plants like less sun, like north or east facing.
If a plant isn't thriving move it to another area of the house. But don't move plants all the time, they're like cats, they don't like being moved! They get stressed. I guess plants in the wild never walk about, so that's probably why! Give them a few weeks after moving to see if they perk up or not.
I've had quite a lot of plants die on me, eg my chinese money plant which I overwatered because I didn't realise it was a succulent!
Another thing I do is whenever I notice a brown or dead leaf or stem I pick it off. I don't let them stay on the plant as they may spread to the rest of the plant. I prune every now and then but not too often.
I would start again with just one or two succulents/cacti in a sunny window and see how it goes, before adding other plants.
IME it's really about the water, just don't overwater most plants and they're usually fine. I have a schedule in my journal of when I last watered each plant (I know, I'm sad).