Living conditions are relatively poor. So when you travel and meet people, you will regret not having some small “thank you gifts” to hand out. We did not listen to such recommendations and deeply regretted this decision.
Things to bring:
Soap, pens, perfume (those small test bottles), shampoo, textiles you no longer use (sneakers, shirts, jeans, etc.). Load up your suitcase with all those little luxuries that we almost don’t even notice anymore. Cubans barely make a living and such goods cost a fortune. Department stores are largely empty and any goods they do carry are largely unaffordable for the average Cuban.
Especially if you travel around, you will meet people and you will regret not having anything to give other than maybe money. You probably want to be smart what to give to whom. Churches might be a good starting point. You don’t want to give presents to children (in no under-developed country). You only risk that they will start begging and chase tourists instead of attending school.