To me, the first consideration in answering your question is to identify exactly what the phrase means. It is easy enough to imagine that the phrase is used to mean that God wants us all to have "Hallmark" (R) moments--"When you care enough to send the very best". When you go to the butcher, God wants you to buy Prime grade instead of choice grade beef, Grade A eggs and dairy, and at the fish market, Grade A jumbo shrimp. Drive an Olds Delta 88 instead of a Chevy Chevette. In other words, God wants us to have the best things. But there is another way to read the sentence. That is, rather than God wanting us to have something which is best on some arbitrary scale, that God wants us to have what is "best for us". Grade A eggs are not best for someone allergic to eggs; Grade A milk is not best for someone who is lactose intolerant; and Grade A shrimp is not best for someone who has a shellfish allergy. And the notion of some kind of objective best is contrary to any number of Jesus' teachings: the lesson from the Sermon on the mount about not being concerned with what to eat, or what to wear (Matthew 7:25-33); the parable of the man who anticipated a large harvest, so he pulled down all his warehouses and built bigger ones (Luke 12:13-21); and the widow who put in a small offering which Jesus held in higher regard than the large offerings of wealthy people (Mark 12:41-44). These passages, and many others like them in Scripture, seem to support the idea that phrase is meant to teach that God wants us to have what is "best for us", not some "best" based on an arbitrary measure.
What, then, is the origin of the phrase? It is not, as far as I can tell, a direct quotation from any the translations of the Scripture with which I am familiar, though I do not claim by any means to be familiar with all of the tens of English translations that have been made. I suspect that this is an example of the somewhat common phenomenon of attempting to quote the Bible without verifying that the passage says exactly what they remember it says. In other words, this is another example like that when people assert that the Bible teaches "Money is the root of all evil". However, the closest the Bible comes to this is 1 Timothy 6:10, where Paul writes "The love of money is the root of all evil." The two sentences are similar, but not identical, and the meaning is significantly different. I take the statement "God wants the best for us" as another example of the same phenomenon, where the phrase is a well-meaning mis-quotation of Romans 8:28a: "We know that in everything God works for good"..., perhaps colored by other teachings of Jesus, e.g. Matthew 7:11, "If you, then, who are evil, know how to give good gifts to your children, how much more will your Father who is in heaven give good things to those who ask him?"
I would distinguish, too, between things that are meant for our benefit, and things that are meant for the edification of God. So I would set having a really good sound system in the Church so that the Word of God is heard better, or God is worshipped better is a different matter from having the very best sound system at home, so as to better hear a sporting event, or listen to one's own music. The former is an offering to God, and is consistent with the commands to make the items associated with worship of God, that is the vestments described for the High Priest of Israel, and the fixtures for Solomon's temple. The latter, to me, is more like the fellow described in Luke 12 cited above.
