Lube. If you do one thing to improve your sex life this year, buy some lube. It's a simple, effective way to improve your sex life. It doesn't cost a lot, and if you're looking for a sexy gift but are a little too shy to get an actual sex toy, lube is a great alternative. Study: Lubricant Users Have Better Sex
Water-based lubes are the most common kind, and are perfect for most situations. Astroglide makes a nice one.
Silicone-based lubes last for hours and you don't need to use much product. Just don't use them with silicone sex toys, which will erode upon contact. Eros makes our favorite silicone lube.
If you want to get into anal sex, choose a thicker lube like Maximus.