I don't know where to start

Having never really babied my hair before, I need some help and I don't know where to start. Right now, it's way too long, but I'm not sure how to get it cut (layers or not, how long, etc). I also have no idea what kind of product I need to be using. Currently, I wash my hair every 2-3 days with cheaper shampoo like Suave or Gardiner, and I usually let it air dry. Sometimes I put L'Oreal root lifting mousse in it when wet and let that air dry. If I have somewhere to be, I'll blow dry it a few minutes while using my fingers to shake it out. I brush it with a paddle brush every day. These pictures are freshly washed, no product, air dried and brushed - my "natural state," as it were.

I have fine hair that's always been on the thinner side. But as I'm getting closer to 40, I think it may be thinning a little? (Honestly, it's hard to tell, since it's always been fine and thin.) It's also wavy, but doesn't really curl naturally. I've only dyed it once or twice in my life (and even then, just highlights), and don't plan to do so in the future; I'm cool with my sprinkling of greys slowly taking over. 😂

As a kid, I usually kept my hair shoulder length. In my 20s I found I looked good with a longer pixie cut, which also fit my "no frills" lifestyle. But now (after 2 kids and 15 pounds I can't get rid of), I feel like a pixie cut or bob would just accentuate my weak chin and rounder, chubbier face.

All in all, lately, I just feel so slumpy and unpretty, and I think my hair is a big part of that.

I'm willing to take some time and put in some work to treat my hair right, but I don't have buckets of money to spend on fancy products (though I will pay good money for a master hair stylist - I go so infrequently). I'm hoping this community can help me find a good cut, and offer some products that work well, and provide me some easy steps to help me have healthier hair that looks decent. I appreciate any and all advice. Thank you!