Biotin is all you need.
My daily multivitamin contains 600mcg, but I take a 5mg (5000mcg) pill daily. I started taking the 5mg pill long before the multivitamin and it worked fine. But 600mcg is not enough.
I've been taking this for nearly 2.5 years now. I've had my nails rip once - after I was off the biotin for about a month two of my nails ripped in the quick because the new growth wasn't strong enough. And I've had my nails shatter once - after using that bull->-bleeped-<- nailcare kit they sell at malls (had a buffing cube with wool/cotton/silk for removing the grooves and adding shine, and a mineral oil treatment for them.) Was playing football/frisbee and a few direct finger impacts completely cracked off several of my nails, requiring that I cut them all off.
I bend them backwards accidentally - it hurts and bruises, but it's fine. I've lost my finger grip on very heavy boxes, resulting in the grip sliding down to my nails before dropping the box, very painful but no lingering damage. I dropped a stack of 10 lawnmower blades on my thumbnail and it was fine. I crushed my pinky alone under 30 pounds of dumbbell and the nail suffered no damage. Caught a boxcutter blade with a thumbnail (no damage) instead of slicing my finger open.

(tip of the nail got cut off in the picture. I need to file them down a little bit and round them out. I shaped them a lot last time I did my nails)
I don't use anything else on them. edit: so if you paint them, use acetone, and other stuff regularly it may not be enough. But for me it's all I need. I get told all the time to cut my nails because it's unhealthy, they'll tear and get hurt bad. The funny thing is that only happens if
you're unhealthy. Healthy nails are very flexible. And yes, having them shorter would mean fewer 'oh god it hurts' nail bends, which happen to me once a month or so, but it's quite tolerable. I can still open cans (side of thumb) and type just fine. Only thing they've done is reduce my ability to apply pressure to pop zits, which is probably a really good thing.