As you may imagine, my nails aren't in fantastic shape due to the constant polish changes. So, I rely upon great base and top coats to disguise my brittle nails. Lately, I've been loving Formula X Smooth Nail Ridge Filler.
Formula X Smooth Ridge Filler ($14, 0.4oz) is a Sephora exclusive, and one of the priciest pieces in the Formula X collection. It's still significantly cheaper than ridge fillers from other brands found at Sephora like Deborah Lippmann or Dior. It's milky white in shade.
Please don't laugh at my awful nails from several months ago. Here's a shot demonstrating how it looks on the nail:
Overall, this doesn't change the tone and you could still wear a mostly sheer polish. I'm not sure how it would work with jelly polishes, but Smooth pairs nicely with most other ranges.
Although its only advertised as a ridge filler, I find that Smooth functions well as a base coat. It prevents nail staining and is a stable base for nail polish. I find that it significantly improves the appearance and performance of my manicures. And at $14, it's a worthwhile investment, especially if you switch polishes frequently.