Pammer-
Are you trying to fit a particular outfit? If not, maybe you could just rethink your wardrobe.
I was a lifetime skinny girl but at 50, cancer added weight (I'll blame it on cancer, not my family's obvious genetic propensity to go from "skinny" to "rubenesque" in the first year of menopause).
I have some dresses that are made of cotton that is a little too thin, so I got some leggings and had my local dry cleaners hem them into "shorts." Never tried Spanx, but I'll guess that leggings hemmed into Spanx are far less effective at tummy-toning, but far better (as they are more forgiving) at bag-toning.
Go ahead and book a few days to go shopping with a friend. It takes a lot of trying-on to get really good at shopping for your body style. Start with color tones, then work toward necklines, arm lines, waist lengths, best belly treatments, best butt treatments... Have you ever seen those women who are 300 lbs but look fabulous? It's not the body, it's the cut of the clothes that make you look like a full-bodied Amazon queen.
I was a tall, thin, shapeless, flat-breasted girl. Looked awkward. Then I figured out the flapper-girl look, and found out that I could wear a full-length shift that fit like a condom that would be obscene with any other girl who had anything more than "Aspiring A" boobs, and I was good to go.
Now, with my new barrel-shaped tummy, colostomy-stretchy-waist requirements, and breasts that got kind of fat so after 50 years of neither wanting nor needing a bra I have to have at least a tank underneath... I'm learning! And shopping!
My point is don't work against what you have, work with it. Start with the most flattering colors (that whole 80's "Color Me Beautiful" with spring, autumn, etc. was actually pretty worthwhile stuff). Then head toward necklines. Never mind the outfit you try on—what does the neckline do to you?
Then arms, then length—gently belted? Two-piece that can still hide a bag? Full length?
I find that patterns hide bags well, but very dark colors do, too. Hours in the changing room.
And, on your special day, if you really feel like the wardrobe isn't good enough, go for a distraction... a dressy corsage, a distracting showy scarf, something to draw compliments. But don't expect a lot of compliments for graduation... everyone is just really focused on their own kids. And your kids will see that you made an effort in your dress or makeup or jewelry or prominence among mommies, and they'll be cool with that.
You'll show up. Lots of parents won't.
Have fun!!!