Agree with a pp you need to break it down and commit to smaller changes otherwise you'll just feel overwhelmed. Can you maybe write down weekly targets for different areas you can commit to? There's no point thinking about losing loads of weight or getting a whole new wardrobe straight away but maybe something like:
Shoes - have a look on Vinted or Ebay. I am someone who literally gets blisters from wearing new flip flops but Brooks trainers are the comfiest ones I've ever had and I never got blisters from them. They are actually specialist running trainers but I don't run anymore but wear these when I walk/gym whatever. They are expensive but you might be able to find a cheaper second hand pair. If not try and go for 'sports'-style trainers rather than 'fashion' trainers like Converse as they'll have more support. Look on Sports Direct website as they often have cheap deals on decent stuff too.
Bra(s) - see if you can go and get measured. I personally prefer Bravissimo as they are specialists in D+ but I admit their stuff is expensive. But they are lovely and won't pressure you into buying anything. If you think you'll be pressured into buying something, leave your card at home. Maybe take £20 cash with you so you literally know you can't spend more than that. Look for t shirt style soft bras for everyday. Look online for non-wired bralettes in sports brands (Under Armour etc.) which are much comfier and don't tend to come in bra sizes so you'd just need to pick small, medium, large etc.
Walking - Once you have walking shoes and a bra, commit to getting out for a short walk every day for a while. It will improve your mind as well as your health so you'll be in a better place to tackle the rest
Skin - I would make an appointment to see your GP as burning sensation from makeup and painful breakouts sounds like hormonal issues and something your doctor should be able to help with. For me, mascara, concealer, a bit of blusher and lip gloss/lip balm is usually enough to make me feel a bit better about myself
Food - healthy food isn't always expensive. Just try to have protein to fill you up (meat, fish, tofu, beans, eggs, Greek yoghurt), fruit/veg/salad and carbs like rice and potatoes as a staple. Don't starve yourself, eat so you feel full and satisfied and use it to fuel your body so you have energy to do your walks. Also increase your water intake if you can which helps as sometimes we confuse thirst with hunger
Finally I'd just say please be kind to yourself, not many of us are totally happy with everything but I do find that focusing on one area usually has a knock on effect on other areas. I hope you feel better soon and start to feel good about yourself 