I've never had problems with running out of keys. They're everywhere. So far to me it seems the bonus items are in the same place. Little bit different enemies, but it's minimal. Of course, the boulders are more frequent, and that's what I mainly got waxed on, but still made a decent score, considering the unfamiliarity.
I skipped upgrading armour, went for the first weapon upgrade, and was heading for the second, but bought it before that with still 800 zenny to go before getting it. I hadn't thought about saving up for the third weapon upgrade. The little I've played it, relatively, I remember needing it, and then by that time there were so much points to be had that the third one was easy to pay for.
....hey, I'm in second place.....