How fit are you? If not very, then increase the amount of walking you do - aim for at least 30 minute brisk walking at least 5 days a week. This will help with weight loss and also with making you feel more positive about yourself.
Take a long look at your diet - could you get some more veg in there? Could you cut out some processed food and sugar? Cut down on booze and caffeine? Increase water intake? Reduce your portion sizes?
I firmly believe that all the most effective 'feel good' stuff happens on the inside - diet, hydration, sleep, exercise.
But on the outside:
Are you interested in make-up? If you are, have a look at Sali Hughes and Lisa Eldridge's websites - they have lots of videos which show you how to recreate different make up looks. Some of the products they recommend are very expensive but you can always find much cheaper dupes in Boots/Superdrug - the S&B crew on here can help you.
I absolutely love having coloured nails - it's one of my 'things' and cheers me up no end. Short, clean, well shaped nails in a colour you like will make you look groomed. You can do all this at home and get great nail varnishes for a few quid in high street shops.
Good luck with it all and enjoy it!