It is generally warm in Cuba, so cotton or similar light fabric clothes should be OK when you travel to Cuba. Just don’t forget to bring a light sweater or something similar if you are planning to travel to Cuba from October to March. In December, January and February temperature could drop to 10-12 degrees for a couple of days, so be prepared. In December, January and February temperature could drop to 17-19 degrees for a couple of days, so be prepared.
From May to October it is rainy season in Cuba, so an umbrella or a raincoat could be useful.
I always wear casual clothes when I travel to Cuba. I find that casual clothes are OK almost everywhere, but it would be a good idea to bring something more formal for fancy restaurants, theater or cabarets. Long sleeves for men and a dress for women will be perfect. A jacket is also common for men.
Bring comfortable shoes when you travel to Cuba. You will probably do a lot of walking.