If it is for a bachelorette: novelty and games, not a toy. It is being opened in front of people, several of whom are related to the bride. A card deck, a coloring book or a plush in cuffs gets the laugh without anyone having to look at the floor.
If you do not know them that well: lube, oil, a game or a set. None of those assume anything about anatomy or experience. A specific toy assumes all of it.
If you genuinely cannot pick: a gift card. It is the honest answer for a person whose taste you do not know, and it beats guessing wrong on something this personal.
If it is for a partner: a set beats a single toy. You get to introduce several ideas at once and let them pick, instead of handing over one thing and watching their face.
If you want it to feel expensive: buy fewer, better pieces. A single well-made silicone or glass piece reads as a real present. Four cheap novelties read as a joke, which is fine when a joke is the point and wrong when it is not.
On sizing: skip anything that needs a measurement. Lingerie and slogan tanks both do. Toys, lube, books, games and candles do not, which is most of why they work as gifts.
On discretion: every order ships plain. No branding on the box and nothing on the label that says what is inside, which is usually the first thing people ask and the last thing they think to check.
On material, if you are giving a toy: silicone, ABS, steel or glass. Non-porous and properly cleanable. Nobody wants to be given something they have to worry about.
