Tipping is not a common practice in Cuba outside of the all-inclusive resorts, but it has become fairly common in these resorts. There is no truly "right tip."  Tipping practices vary from one individual to another, and from one culture to another.

For some thoughts on the subject of tipping, you can read the following article, which is intended to summarize the tipping practices of a range of the contributers to the Cuba forum:

Tipping

Try to use a few Spanish phrases when speaking to the resort staff. Simple things like por favor or gracias (please and thank you)."

Buenos Dias  for good morning,  but it is polite to add señor for men or señorita for the ladies.
Hola is the informal greeting,  much as English speakers might say Hi.

An inexpensive phrase book and a little effort will make your experience even better.  The Cubans are used to lazy travellers who don't bother  learning even the basics,  so  when the effort is made,  it is very much appreciated.

For the smokers, it's a beautiful sandy white beach and looks a lot like the sand you see in ashtrays at hotels but this doesn't mean the beach is your ashtray.  Take one of those plastic cups you got a drink in, put in some sand, and when you want to butt-out, do so in the cup.  Then when you leave the beach, toss the butts or the cup in the garbage. The beach is for everyone to enjoy please respect that.

Just remember the simple principle: Be polite and courteous.  If there's a dress code, please observe it.  Take your ballcap off at the table (for all meals).  Respect is universal. Don't make a mess at the table, or in your room.  There is no need to make the staff's jobs harder than it already is.