Angelat-what are you wanting to improve with your nails?
Prostong -tried it didn't like it, the polish has to rank as the worst I have tried- didn't stay on for the day. Think this is another one 'only' sold on QVC.
Agree with Leighton Denny about Crystal Files - somehow they seem to 'seal' the free edge of the nail so if nails are flaking because water is getting into the layers it seems to help. He suggested on a recent show to try this before treatments, which I thought was interesting as he sells treatments, so he must see it helping people when he is working with them, because he could equally be selling his treatments.
I use an OPI crystal file which I love (would considers Leightons as I think his may come in a wallet to protect it where as the OPI is just in a plastic tube) & Creative Nail Design - Cuticle Eraser, a really gentle AHA based cream that keeps cuticles moisturised, keeping the dry skin around the fingers at bay. I think the CND also helps moisturise my nailbed. Bought both via ebay US-make sure the purchase total is less than £18.00, if you decide to go down this route.
I did try Nailtek II Foundation as a treatment\base coat - but find I no longer need to use this. Although I do like and use their Replenisher\Hydrator that I use as a topcoat.