Another chirp about DDB and sharing subscription, which we use for all our 5e play. We also implement all of that in Foundry VTT -- and I pay for Mr. Primate's DDB Importer (which is awesome) so it all works out.
I have also purchased Tasslehoff's Pouches of Many Things, the DragonLance Companion and DL - Peoples and Paragons, all off of DMs Guild. I am making selective use of that material. Though there is a LOT of material that is quite useful in these three books, I draw particular attention to the Piety system in DL Companion as well as the additional Knightly Disciplines in P&P to help further differentiate and enrich my Knights of Solamnia. Subclasses and more races and spells is not something that concerns me (and I don't plan to use any of it) -- but when it comes to this stuff, YMMV (and often does).