So sorry to hear about your wedding. Your dress sounds lovely.
You could start by upping your water intake. This advice gets wheeled out all the time because it works. It will help your skin and in a strange way lifts the mood too.
Do you exercise? If not, try adding 20-30 minute work out for at least 3 times a week, if you can manage daily even better. You could go on You Tube to find Pilates videos to tone up or you could try Jillian Michaels 30 Day shred Level 1. Or at least walk every day, walk very fast.:-)
Body brushing in the morning before shower will help to tone up your skin and will wake you up. Use a body lotion or oil as soon as you get out of the shower. When your skin is slightly damp, it will absorb very quickly. Dove and Nivea do good toning body lotions.
Body Shop has a good body brush. Here is how to do it goop.com/how-to-dry-brush-and-why-its-so-potent/
For your face, in addition to cleansing and moisturising, use a cleansing mask and follow up with hydrating mask at least twice a week. If I have an event to go to where I need to look good, I use the hydrating mask every day 4-5 days before the event to plump up my skin. I apply it first thing in the morning, brush my teeth, have a shower, rinse it off.
I like this
www.lookfantastic.com/vichy-pore-purifying-clay-mask-75ml/11318434.html
and this
www.lookfantastic.com/la-roche-posay-hydraphase-intense-masque-50ml/11091834.html
For your hair, use a hair mask 1-2 a week to improve the condition and get a trim or a cut. Currently I am using this mask and my hair is soft and shiny. My hair is curly and dry so if yours isn't, check out the rest of the range. They have masks for different types.
www.boots.com/Loréal-botanicals-safflower-rich-infusion-masque-10225842
Hands and nails. You could by almond oil in Holland and Barret and massage it in your cuticles and nails every night, then apply a thick layer of hand cream just before you go to sleep.
www.lookfantastic.com/hand-chemistry-extreme-hydration-complex-100ml/10985288.html
or this if on budget
www.boots.com/nivea-q10-plus-age-defying-hand-cream-30ml-10114310
Can you book yourself for a manicure and pedicure before the wedding?
If you don't have time, budget or inclination to do all of the above, I would pick drinking lots of water, walking and dry body brushing above all. It will make you feel good and if you feel good and confident. Good luck!