I'm an 18-20 in my 40s and I regularly receive compliments on what I wear and how I wear it. Biggest game changer was stopping trying to wear the same as everyone else. I've been size 10, 12, 14, 16 too and I've always felt my shittest when comparing myself to slimmer friends in similar outfits. This way madness lies.
It is hard to dress a belly. That's been the hardest element of choosing clothes in my current body.
Jeans often look shit on me and they can be very uncomfortable so I'm pretty picky. Best for comfort, shape and size for me has been Snag - the people who make the tights and the chub rub shorts. Those jeans are very comfortable and I wear the black pair loads as I can dress them up or down.
My fave brand for clothes available in a wide range of sizes is Never Fully Dressed. It can be quite spenny but often comes up on Vinted, or you can get a limited selection via Next or Asos and spread the cost monthly or use Klarna. They use a mix of models so it's easier to see how stuff looks on different bodies (and ages, skin colour etc). Alison Hammond and Andi Oliver have worn a lot of different outfits from them in recent years.
And I now prefer to spend on something I love that I can wear over and over and in a range of ways than something cheap that I don't enjoy wearing as much.
Another thing that really changed how I dressed my body was switching my mindset away from thinking I only deserved nice clothes when I got smaller or buying clothes for a special event in a smaller size as motivation to lose weight. That stuff SUCKS ARSE and can get in the bin. Buy clothes for the body you have right now.
Belly and curve friendly stuff that I love and that feels fancy but is also comfy tends to include satin skirts or dresses cut on the bias so they skim rather than cling. Pair with a fun tshirt for a casual look, a gorgeous coloured wool jumper for the winter or a lace camisole and blazer for a meal out.
Agree with DorsetKnobBiscuit about bras - it's about making sure they fit you correctly. It's annoying but worth it and when I find a design that looks great and fits well I just buy it in a range of colours so I can mix things up without having to go through the rigmarole of trying different brands on.
Knowing your style and colours helps too. What are you into? Something with a rockier edge or something more whimsical and feminine? For me, that's what makes the difference between something feeling right or wrong on me. If it's too frilly and froufrou it's just not for me - could look amazing on someone else but I feel weird and wonky and like I'm playing dress up.
Also - joggers, tshirts and trainers are not all the same. An outfit of joggers, tshirts and trainers could look really cool. I follow a lot of dopamine dressing accounts on Instagram and comfort is king.