Such a hugh range of products and also a number of areas to target! What sort of items are you considering? I'm anything from size 8-12 depending where you buy from so generally a size small in clothes. I don't need a lot of support but like a smooth line under clothes.
I've tried on most of M&S stuff and haven't found anything that does the job in my budget. Pants either do the job on the waste but cut into your butt or give dig in below the belly button, or just don't offer any support at all.
Primark stuff as mentioned on other threads on this site seemed OK and value for money but I didn't buy any. Never seem to have a small enough size in store near me and quite long in the body so could pucker I thought but at those prices I would suggest giving them a go.
I've given up trying to find pants that really support the buttocks but the best I have came from QVC, a TSV from Slim and lift long line pants.Item 105955 but only available limited sizes now. Personally I would maybe buy a 2 pk the longer ones anyway 153320 at £40.45 inc p&p.
Waste wise the best has been Debenhams, £20 I think for one of those that goes under the bust and down over the hips. It has a tiny bit of boning so it doesn't ride up and keeps you gently sucked in;and it doesn't show under sheer fabric. I have a black one but they do a nude colour I may buy when I can splurge.
Bras without underwire are everywhere. Next do a thin strap slightly padded none wired bra for £12, just in black and white though;and unlike alot of these 'beauty bars with thick straps it doesn't show under everything.
I do like the the Ahh bras everyone does, I'm small on QVC but medium on idealworld.
Idealworld also do thin strap cami's (item 241 549 £9.99 on sale)I think are excellent that don't ride up on me any more than a cotton T and are great under sheer shirts or tops and do give a bit of a firmer support around the waste and gut. Just order in a couple of sizes to start and pay for a 'click and collect' return label at £1.50.
There's no short cuts with these things. Type of fit and comfort for our individual body shapes is so personal you do end up having to try on a gazillion things! Good luck. Hope you find what you're looking for, let us know what works for you.