Hi OP, great thread I love a makeover!
My first observation is how you’re talking about yourself. You said your hair is “oil slick” black, skin is “sallow” you dress “like a man”. My love, please please be kind to yourself. You aren’t going to feel good about yourself until you tackle this negative self talk. Actually the other things don’t matter anywhere near as much as this!
Other than your outlook my tips for “the outside” are as follows:
Hair- expensive option is to get a cut and colour. Cheaper option would be to cover greys with a home dye similar to your natural colour. There are YouTube tutorials on how you can trim your own hair. Or maybe you have a friend who wouldn’t mind snipping off a centimetre or so just to trim the dead ends?
Hair styling- you’ve said you have frizzy/ curly hair. Honestly, I have the same hair type and straightening it is so much quicker and easier than the curly girl method! I’d buy a cheap straightener and wash dry and straighten it a couple of times a week. I’m so quick at this now and you’ll get quick too- promise!
Eyebrows- pluck any stray hairs and trim of out of control.
Skin- go to the doctor and get some nhs prescription soolantra. Not expensive of an nhs prescription. Other than that Lidl do a good day and night cream for a couple of quid a pot.
Teeth- Crest whitening strips are cheap as chips and you can buy on Amazon. Use them for a couple of days until your teeth are brighter. They do damage your teeth but quite honestly so does drinking coke and eating chocolate. It’s all about balance.
Makeup- I have rosacea and I use Dr Jart Cicapair treatment https://www.boots.com/dr-jart-cicapair-tiger-grass-colour-correcting-treatment-50ml-10292009 If you used that, some liquid bronzer (so as to not add to the redness), some clear lip gloss and some mascara that would be a good start!
Body- start with the basics. A loofah to exfoliate in the shower, shave fuzzy parts and a bottle of nice scented lotion.
Nails (hands and feet) file and shape with a nail file. Clear or skin colour polish. Moisturise your hands and feet with the lotion. You might need a foot file depending on your foot skin.
Fake tan (?) you haven’t said your skin tone but assuming you’re white from your comment about having “sallow” skin? I honestly find that a layer of fake tan really makes a difference to my overall glow at this time of year. But might not be relevant to you, so ignore if you’re not pale.
Clothes - so hard to say without knowing you but at this time of year I live in tights, leggings, boots and dresses. If you were on a budget you could get one decent pair of winter boots from Vinted, I’d go for flat and black leather and a bit more dressy than doc martens so they could be work for day or night. Then 7 pairs of opaque tights, 7 long/ midi dresses in dark, classic colours (example linked). Assume you already have a winter coat and a handbag but you could look for other versions. I feel like this outfit could work for day/ night and lots of jobs. Practical for dealing with housework and kids. Dress: https://www.marksandspencer.com/jersey-sparkly-ribbed-midi-column-dress/p/clp60705200?intid=mobile_app_pdp_share
Wellness- focus on free/ cheap stuff like going on a walk, eating fruit and veg and drinking more water. I know you say you have no time and I get it. But everyone has time in their day to do a 10 min yoga video. It’s free, takes 10 mins. No need for shower after and you can do it on your PJs! Yoga not your thing, try Pilates, HIIT etc. Also remember exercise is not about “burning calories” it’s about treating your body well and feeling good.
Good luck!