Hi. I'm a TA who has MANY Virgin clients and sails Virgin myself.

There is a bar calculator at this independent site: https://vvinsider.com/bar-tab-calculator/
Lots of helpful information.
If you find near the end of the cruise, you have too much bar tab, you can buy drinks for new friends, if you see crew off duty you can offer to buy them drinks, or you can start drinking expensive drinks you would otherwise never try like $50 shots. Avergare glass of wine price on Virgin is $9.00, average cocktail is $14, average bee is $8.00.

For mingling, you will get invited to a solo traveler meet and greet the first night. There will be a note in your stateroom. Often it includes dinner. Go! They often then set up chat groups for other get-togethers.

Other suggestions for meeting others:
Go to Gunbae early in the trip. You are seated with 6-8 people and they have a fun ice breaker.
The Grog Walk (extra fee) is good for meeting kindred souls as is Looto Gigante (lots of fun)
Also, go to games in the social club like trivia and speed jigsaw puzzles.. You will usually be placed with 4-6 others and you'll have a chance to meet others.

Finally, there are often roll call groups on Facebook, Cruise Critic, and the Subreddit r/virginvoyages.

Have fun!