I’m in my mid-30’s and had a similar realisation.
I’ve been gradually updating my wardrobe from cheap poorly-constructed polyester to more high end brands like Cos, Reiss, Boden. I buy expensive things preloved. Good stuff can be found in H&M and Uniqlo if you look for 100% linen or cotton.
Figure out your colours and shape, look up the relevant capsule wardrobe, and buy ONLY those items. Sounds boring but the result is good. Pinterest and YouTube are good resources for ideas but figure out what you feel good in.
Exercise and track calories. I’ve only been doing this for 2 weeks and have already lost 3 kg without pain. Goodness knows how many calories I was eating beforehand.
Figure out what exercise suits you. I previously did a lot of cardio (running) but it made me overeat. Now I do 20 mins of weights 3 times per week, no cardio, and it’s doing wonders. Not making me hungry, but toning me up and probably increasing my metabolism a little.
Skin is really important. I’ve been using Dermatica for 2 months and really see an improvement which is great for my confidence. Other brands are available. I don’t use foundation. Only moisturise generously and apply spf every day.
Download a fashion/beauty podcast. If you’re interested in fashion then it becomes fun. I enjoy thinking about my clothes and accessories now. Probably nobody else has noticed my effort, but I feel much more confident if I’ve made an effort and that makes me more assertive and sociable at work.
Good luck!