Lubes, probably, on the least exciting things to buy from a sex shop. Honestly, they go long with the good stuff. However, a good lube can increase the ease of using toys, a must for anal play. Some can be flavoured for extra flare during oral sex. Others can warm or cool.
K-Y is probably the most classic. It’s available in the “family planning” section of any drugstore. The reason it's a classic is its no-frills approach and its hands down a great relabeled product.
This was the first lube I ever used, and 20 years later it’s still a staple in my lube drawer.
The start got a great slipping texture. Easy to apply, lasts well. Clean up is a breeze with mild soap on yourself or toy cleaner on your toys. I have never had any issues with irritation or rashes. No foul smell, and if it gets in your towels and sheets, it washes out with no permanent staining.
I highly recommend this item.