I have those horrible dark spots. I've been using factor 50 on my face every day for 3 weeks.
When you say you don’t usually leave the house - did you mean you sunbathe in your garden?
More generally:
Getting outside as much as possible, beyond your home, will improve your physical and mental wellbeing.
Do you get much opportunity to speak to a range of people - including strangers? You can do anything you want to alter / improve your appearance but in order to enjoy the event you’re attending you need to feel at ease in a social situation. The worst thing about being confined to home is how painfully self conscious one can feel when you do eventually go out. So it would be a good idea to create ways to interact with strangers and groups over the next few weeks, so it’s less of a strain on the day.
You really don’t need fake tan or fake nails - though you can get them if you like. In social situations people need to look clean and tidy, smell fresh and show an interest in the people they meet.
Dentists are expensive but if you can afford a visit this might be money well spent if needed.
Get a weekly veg box with probably three times the amount of fruit and vegetables you may usually consume. (Obviously if this is something you do already, that’s great.)
Avocados, carrots, fresh turmeric and salmon may make the biggest difference to your appearance in the shortest time if consumed regularly. Eat things in as close to their natural state as possible - you don’t need complicated recipes.
Oh! Order some enormous bags of magnesium salts (not dainty little jars) and throw several handfuls into a bath a few times a week. Miraculous effect on skin and great relaxation properties.