I’ve struggled with paper-thin nails all my life, good tone is hard to achieve; following painting numerous coats of nail hardener, rubbing almond oil in, changing my diet, eating copious amounts of jelly, I eventually gave in and bit the bullet having them coated in acrylic gel - now that they are rigid I can create a decent tone, which the embarrassment of visiting the nail bar doesn’t outweigh. I have been spotted there a few times and always stress very loudly "it’s just the one hand as I’m a guitarist". I wouldn’t advise gel as once you’ve started, your nails are ruined, but I felt I had no option… I do try to let them grow out a little so that roughly half the nail grows uncoated, much to the dismay of the nail bar guy who always tells me off.
The debate over flesh or nail, or flesh and nail is endless (do a Google search, the heated debates are scary). To sum up: flesh for gut strings, flesh and nail for warmth with good articulation and a decent tone, just nail for an ultra articulated, thinner sound… there you go, can of worms well and truly opened.
Whatever the case, it’s good to become obsessed with tone production. Beyond a basic level, it may be necessary to switch from the standard flesh/nail stroke to employ either just flesh, or just nail, to add contrast within a piece of music.
I'd advise that beginners start without nails, but once a guitarist is beyond the beginner stage and pieces become more demanding with a wider range of tones required, it is important to allow the nail to grow just beyond the tip of the finger. Good tone though is dependent upon a highly polished edge (so that the fingernail glides over the nail effortlessly) and a good finger angle, the video explains the process.