Glass cleaner got expensive for me when I installed replacement windows for a living. Unlike most installers, I washed the windows at the end of the installation. I thought why would the homeowner want a bunch of manufacturer stickers on their new windows. On that subject, you'd be surprised.
So I made my own. Start with a gallon of distilled water (not necessary but it makes the final wipe really clean). Add one ounce of ammonia, one ounce of white distilled vinegar, one ounce of isopropyl alcohol, a thimble of Simple Green (or other similar, but it has to be as nasty as SG is) and a dozen drops of liquid detergent.
Now there are 2 million recipes that are similar so just take the idea in stride and make some with what you have on hand. Mine would cut the factory oils on the first go round, and with a new towel it would do a perfect job the second time. Yes, wipe in different directions inside vs. out.
For me, if I saw streaks or smudges, I did it one more time and if they were still there in the sun it was time to call for a glass change out on warranty. That happened a few times and I was able to show the rep that there was no way the exterior surfaces weren't 'squeaky' clean.