CND one is the best by millions of miles. Don't bother with anything else.
After removing nail polish and shaping, squeeze this on your nail bed, massage in, listen to your favourite song and then push back gently with a cuticle stick. Don't ignore the stick stage. Wash your hands with a grainy soap so you exfoliate a bit. Then meticulously clean your nails with nail polish remover and get right in the corners. Then paint. I've been using this for about three months and my nails have never looked better.
About painting your nails, do not paint too close to the cuticles. Nothing gives away a home manicure like manky, messy painted cuticles. With this the job is much easier but even then, don't go to the nail bed. I find painting nails easy because I've basically spent 35 years practicing. I spent much of my childhood bored on Sunday afternoons and so I used to paint my nails all the time. I was terrible to start with but now, I swear I could be a nail technician although I've no idea about nail art. The easiest brush is the YSL one, I know they are expensive but they almost do the job for you, utterly foolproof.