OK first of all, few people are genuinely ugly. Some are better looking than others, that's not the same thing.
But cheap things you can do if you need an appearance boost - hair, if its greasy, can you look at which shampoo and conditioner you are using? Are you using too much conditioner?
Drink more water. It honestly makes such a difference to the haggard look thing. Make sure you are eating a range of fruit and veg so you are getting enough vitamins.
Posture, if you are picking plain clothes so you don't stand out, is your body language all slumped? Posture and help so much.
If the "mum tum" is an issue, thats something you can easily work on. Losing weight might really help your confidence.
Do you own make up now? If so, find 5 minutes each day to put a little on.
If your budget doesn't stretch to new clothes, can you look at what you already have, if you lost the excess weight, are there other things that will become possible again? Do you wear jewellery? Sometimes just stopping to think about adding a bracelet or different earrings can make you feel better about your appearance and that confident feeling can make you look better.
Be kind to yourself.