Oh how dare you feel confident enough to smile at a man OP! Got to slap you back down eh?
I have two states, smart and scruffy AF. Walking home from work, smiling and with a spring in my step because it's Friday afternoon and I'm free for the weekend, dressed smartly, hair done and a full face of makeup. A group of lads drives past making suggestive comments, beeping the car horn etc. Half hour later I cycled to the stables to see my horse, dressed in faded joggers with holes in, a stained and frayed tee shirt that doesn't match, hair quickly scraped back in a pony tail and with the makeup which was starting to melt half wiped off with a tissue, serious faced huffing and puffing as a scaled a hill. The SAME group of lads drove past making derisive comments and calling me names like "minger" etc. They didn't recognise me, I didn't exist to them, I was nothing more than my visual impact.
It's not you, it's them. 💐 OP. They're totally shallow and incapable of seeing A Person when they look at one.
To answer your question, if you want to change for yourself, go for simple things you can manage with your lifestyle. Declutter any faded, stained, frayed, badly bobbled or holey clothes. Also those which don't fit, which you find uncomfortable, the colour doesn't suit you, or it's lost it's shape. Find simple outfits that match your lifestyle, in colours that suit you and a size/cut that fits you. An "everyday uniform" if you like. It doesn't need to be more complex than a simple dress, or jeans with tee shirt and cardigan. Get boots/shoes, handbag and a coat that matches all your outfits, this takes away any decisions about which one to wear and prevents you getting it wrong. Have enough clothes that you can get changed if you're covered in baby sick or something. It's easier if all tops match with all bottoms, takes the thinking out of it and you'll never look mismatched because half the outfit is in the wash. Get underwear that doesn't make you sigh with depression when you look at it. You don't need those knickers with the saggy elastic or those socks with the holes in. You're worth more than "making do". This is how you look polished from the outside and feel confident in your outfits.
Drink enough water and take some form of exercise, even if it's just walking in the park with DC. Eat proper meals including vegetables and limit unhealthy snacks. Consider taking a general multivitamin and mineral supplement if you feel it's necessary. All this will make you shine from within.
Have a skincare routine. Clean your face, apply some serum, some oil if your skin is dry and some moisturizer containing SPF. Wear whatever makeup you like. If you want to wear any at all, it's not compulsory. If I'm short on time I swap ordinary moisturizer for a tinted one, use a brush to quickly put eyeshadow onto my eyelids and a quick coat of mascara, tinted chapstick for my lips. Take it off every night before bed and apply moisturizer. You probably don't have much time, so you need a hairstyle that can be washed, combed and left to air dry. And not require a trip to the hairdresser every 4 weeks to maintain it. Wash your hair when you need to, use leave-in spray conditioner if time is short, comb it daily (unless curly. If it's always a frizzy mop it's probably curly and you don't realise, so put down the hairbrush and leave it be, scrunch some mousse into it after washing/combing conditioner through). File your nails neatly. That's all you need for finishing touches to make your skin/hair glow.