MadMomma I was you 18 months ago and it was just horrible, I had totally lost myself.
My advice is to keep it simple, little steps at a time. Better to make little changes that you can stick to and build on in time than to make big changes that fall by the wayside.
How I got started:
Drink more water, start with a glass by the bed and drink it when you first wake up, more through the day. I used to have mine in bottles so one was always to hand. I think this made more of a difference to my skin than any products I bought did.
Buy some cleansing wipes and a good moisturiser, keep them by the bed if you think you'll forget to use them otherwise.
If you still have some knocking around from the babies, Johnsons Top to Toe wash makes a really good face wash, its pH neutral, hypoallergenic and really mild so suitable for most skin types.
This from Estee Lauder is amazing. it made me look human again and like I'd had some sleep even when I hadn't, its pricey for me but was more than worth it.
Keep a small make up bag and keep just the very basics in it. A good foundation, a blusher and a lip colour/gloss etc. You can do the basics then each morning and look good. Save the more faffy stuff for when you are more in the swing of it.