Keeping a pleco tank?

Alright, I have dwelled into the realm of the scaly wet ones instead of the scaly slithery ones. So I figured I would ask a few questions.

I have a 50 gallon tank that I am keeping plecos in, all of the plecos that I have are different morphs of Bristlenose (longfin, shortfin, and colored), a clown, and a rubberlip. So all the ones I keep stay smaller than 6 inches.
I also have some khuli loaches.

What I would like to ask is how to successfully maintain live plants? I have some, but they all look worse than when I got them and are falling apart lol. I am not much of a green thumb.

Also, what is a limit as to how many plecos I can have in this size setup?
I know they can be territorial, so I have plenty of caves and hiding places of plastic or driftwood.

So does anyone know what plants would be good to keep and are easy to keep as well? Thanks.