Pepper, I suppose you're right. I'm a 36-24-36 at 5"4' which looks pretty average in my estimation but by many is considered a 'perfect' hourglass (which I find a very troubling term) but even when I was larger (retained the same ratios) the same rules applied. I wasn't all that quick to tuck in tops or shirts into trousers though, that's something a lot easier to do if you're smaller. At this size, I'm also less arsed about looking a size or two bigger. My ankles and wrists are also slight so it can handle the balance of a bit more volume in cloth. I've attached a pic of the type of look I meant above, figure it's a handy reference, basically low rise jeans to emphasise length in the torso (in my case that often means a mid rise worn as low rise) with a larger shirt tucked in, usually a premium material. Sometimes I knot the bottom instead of tucking in, for variation I also wear it with buttons open down to the waist with a lighter colour vest underneath which also work well optically.
I think the crux of it often is that hourglasses often tend to gravitate towards things that look like their shape, like the above tops, but those things are usually designed for other body shapes to mimic the hourglass curves. I've long relinquished the mantra of 'must show off my waist', or curves for that matter. I always look for vertical lines (think plunging necklines, I'd wear them down to my belly button if it was considered decent) and height and that shows off my hourglass figure subtly rather than very overtly screaming here's my boobs + butt. Technically I'd look my best in very fitted clothing (and for coats, tailored pieces, dresses, etc. I do buy into that and isn't challenging at all but it usually means you're quite over-dressed) but it's not exactly comfy or casual and can veer into that vintage retro look which I personally do not like on myself.
Gah, have you tried Paige denim? I'm a bit tepid about J Brand (I only really like the ones in the Photo Ready Finish) and really rate the Paige fit, especially the Transcend versions which are made with comfort in mind.
For t-shirts, thought of a few more, not exactly low budget, so apols in advance, I tend to stock up in the sale. French brands work well for me (may be a height thing too though) but APC, Isabel Marant Etoile, American Vintage all do something uniquely flattering in the waist area without being massively tight and form-fitting. On the budget end, I've found this one from Weekday v. good in a variety of colours. Mine are cotton though so not sure how the fit would be now.