The sale, if it works previously, is great because you can combine media too and their usual record prices are low enough to be good deals at 30% off, then you can usually get free shipping and Red Card discounts and the like.
And I agree, the big box sets are the best bang for the buck but really any three records, if Target is priced in the realm of everyone else,, will likely represent good savings. It's worth running through artists/titles on your want list in advance and hearting them for easy access. Like, people have been raving about the REM New Adventures - its $34 before any discount which means you can bring it down to the mid 20s or so if you have other items. It's all about finding items that don't get priced down much elsewhere or, as suggested, the box-sets for sheer volume.. Looking at my favorites, I have a handful of 15-25 dollar albums I'll probably make a trio out of for this sale.
But yeah, like even without the trick, something like the Joni Reprise Albums, Grateful Dead Box, and Hamilton OST for $170ish is probaby lower individually than you'll see those boxes if you split them out and that's even without the trick.