Lots of free things you can do- walking or running for fitness, yoga and pilates vid on youtube for toning and posture.
I've found that any alcohol at all these days (I'm late 40s) goes straight to my face, sadly- dry, blotchy, red etc. Cutting that out has made a huge difference to getting a glowy look. Also skincare pays off at my age, esp a decent sunscreen.
Go for a consultation with a personal shopper- lots of places do them for free and it can be a good way to get new ideas. I also find the website Thread good for that- you can put in your size and the things you like and it gives you lots of ideas. I have yet to find anyone doing post 40 fashion on Insta who doesn;t massively annoy me but you may have more luck. I think post 40 a lot of things that used to work when younger can stop working, eg as a 90s kid I used to love a floral tea dress like Kate Moss or boho a la Sienna Miller, but sadly as I've got older things that were once young and cool on me now make me look ancient, less Sienna Miller and more Windy Miller 😭ressing like a little old lady only works when you're clearly 22 max.
Same with make up, get a free makeover done for some new ideas. Heavy foundation is v ageing.
A thing KM does is buy high street stuff and get it adjusted, buttons resewn etc, so she looks in touch with ordinary people but also somehow smarter. For that sloaney look, a couple of good blazers are a good buy and can go with everything. Have a look at Sezanne. Jeans that suit you rather than following fashion. It's quite easy to get that look with quite a small capsule wardrobe, to be honest, as it's v uniform-y.
I also think very small things can make a difference. For me, spending just 3 minutes doing make up in the morning helps- I just do concealer, cream blush, cream eye shadow, mascara, tinted lip balm. I am trying to train myself out of the mum-bun habit but it is hard!