Target's Threshold Cotton Percale sheets are pretty good, and very reasonably priced for what you get. We bought three sets about a year and a half ago, and outside of needing to hit the edges with an iron occasionally, are holding up very nicely. They remind me of the quality of sheets you used to be able to find more readily 30+ years ago. I'm also pretty sure, they were a recommendation by others here as well at the time, though I can't remember who.
Beyond that? Most threadcount ratings (especially luxury-targeted) are meaningless at best and garbage at worst past about 300, with astronomically higher threadcounts actually not holding up well. Stay away from synthetics, novelty fabrics, and outlets like Marshalls/TJMaxx/etc. with "fancy" name brand sheets... unless you know for a fact what you're actually getting and what to look for, but even then, the price usually isn't worth it as you're paying not for the quality but the name. Good no-name sheet sets cost around 2-3x the low-end, but the high-end cotton is either name brand cache or marketing buzzwords. Pay attention to the weave, quality can often be seen in it (why I recommended percale).
Hope this helps!