I've been on 7 cruises over about 25 yrs. I've never heard of an alcohol drinks pkg. The drinks are usually quite expensive but I don't drink much so I don't care. If you like wine some cruises let you purchase the bottle at dinner, then they'll store it for you and bring out at dinner when you want another glass. Some allow you to bring wine aboard and charge a corking fee to serve it to you. That's handy if you find some wine in a port that you'd like to try. I've known people to pack a bottle of booze in their suitcases and mix drinks in their room. It's not usually allowed but they are so busy trying to get everybody's luggage to the staterooms that I've never heard of anyone getting caught.
Usually there's one or 2 formal nights. Even a nice dressy pair of slacks with a dressy looking blouse or sweater and jewelry is acceptable on most cruises. Usually the cruise's website will have a link to "What to Wear". Most cruises have a meeting on the first full day to discuss the itinerary and things to do while ashore and most will sell various tours but you don't need to buy one if you are comfortable exploring on your own. You often get maps of the ports and good guidelines to keep you safe.
If the ship is large there will lots to do on board. Most will put a daily schedule of events in your room each night for the next day or have it on the TV monitor so you can choose what you would like to do.
If there's a chance you'll get seasick, go to a DR. beforehand and they'll give you something to prevent it.
And don't overpack. Plan your clothes so that the colors go with each other so you can mix and match and make several outfits out of few clothes
Most of all, relax and have fun!!