Hi Chari and welcome to Cruise Chat.
The casino on Sovereign of the Seas doesn't seem too crowded at the tables. We're not big casino users, but I've never noticed people standing around, waiting for a seat to become available. If you go during a day at sea, the crowd is pretty well spread out on the ship. If you go in the evening around dinner time, changes are half the passengers are in the dining room if you go before or after your dinner time.