A small host gift with fewer assumptions
A small gift should not give the host another task while guests are arriving.

A host opening the door may also be watching a pan, finding chairs and introducing people who have never met. A gift that needs an immediate vase, refrigerator space or an explanation can land at the wrong moment. Think about what happens in the first five minutes after you hand it over.
Something ready to put aside is often the easiest choice. A clearly labelled food item, a small packet of tea the household enjoys or a simple kitchen cloth can be received without rearranging the evening. None of these is universal: preferences, allergies and the household's habits still come first.
Food is an offer, not a new menu
Ask before bringing a dish that you expect to be served. The host may already have planned quantities and dietary needs, and the refrigerator may be full. A present for later is different from a contribution to dinner. Saying which one you intend removes a surprisingly common uncertainty.
For packaged food, leave the ingredient and storage labels intact. If you made it yourself, tell the host what is in it and how it has been stored. Do not present an unfamiliar item as suitable for a dietary restriction unless you can support that claim. A non-food gift may be simpler when you do not know the household well.
Keep the gesture light
There is little benefit in choosing a gift so large that it becomes the centre of the visit. Consider whether it can be carried home by public transport if you are meeting somewhere else. For someone who hosts regularly, another serving object may duplicate what they already own; a replenishable item they use can be more welcome.
A short handwritten note can explain the choice without a long speech. Avoid asking the host to open everything in front of the group or report later on how it was used. The gift belongs to them once given.
If the invitation says not to bring anything, respect it. You can thank the host afterwards without buying an object. Good manners do not need to become a shopping requirement every time someone opens their home.