Hi, welcome to Goa. There are different places to visit in Goa depending on your taste. you can visit beaches - I always suggest visit one beach in North Goa and one in South Goa. it should be sufficient.
Goa has some beautiful forts- Reis Magush fort near Panjim is really good. You can also visit Aguada fort.
You can visit Churches in Old Goa- it's beautiful architecture. Goa also has some beautiful temples like Mangeshi. basically it depends what you like. I would personally be happy to show you Panjim, if I am in town. Do let me know when you are coming. I am happy to show my Goa to new people.
I've been recently to Goa and will suggest you to avoid going goa in this season as it's too hot and humid. Anyway if you want to go, the best places to travel will be Aguada fort, Calngutte beach for water sports, Old churches in south Goa and do try going on Paradise Cruise. Also, try getting a hotel near to a beach so that spending some quiet time at beach will be possible in early morning and late night.