Would echo the comments about investing in good skincare. It doesn't have to be £££ - shopping carefully makes a difference. I haven't tried The Ordinary (but thanks to the PP for the tip - am off to get some this aft!) but I have been using the other Hyaluronic products from the company (Deciem) and they are very good.
In no particular order:
SPF - always wear some on your face as it will help your skin in the long run. Clinique Cityblock is good as it's also tinted so can double up as makeup. It does leave a 'dewy' finish though so you may want to finish with a dusting of powder. If you are tired around the eyes then avoid your eye area as powder will settle in the fine lines and emphasise them.
Good skincare routine - Caroline Hiron's website is a good place to start. Her 'cheat sheets' contain the basics for what you should be looking for. A minimum would be good cleanser + toner + serum (the Aldi Lacura ones are good if you are on a budget) + eye cream + moisturiser to finish. The toner you need will depend on your skin type - CH's website will explain this.
Good concealer. I bloody hate Touche Eclat - have always found it chalky and very drying, but others swear by it. I've used all sorts from cheap to very expensive but keep going back to Boots Collection creamy concealer - which is under a fiver and really good for under eyes.
Eyelash curler - sounds like a faff but it's a few minutes well spent as curling your lashes does open them up. Getting your brows properly done to suit your face shape is also a worthwhile investment. I went to a salon as a one-off and have then just maintained it at home myself ever since. Once a week pluck to tidy things up and I use a tiny bit of shadow to fill in any gaps - the Sleek (from Boots or Superdrug) brow kit is very good for this.
Blusher - quick sweep of colour helps you look a bit perkier. I absolutely love Sleek's rose-gold blusher (which is a dupe of NARS 'Orgasm' at a fraction of the price).
Drink - more water, less caffeine and not too much alcohol. Sleep's a bit redundant at this point as you have your hands full(!), but lots of water and herbal teas if you like them, will help keep your skin hydrated.
As others have said though, at this stage you've got other things to concentrate on - so don't be too tough on yourself!