I've never seen anything in published material do so, which makes me think I'm wrong, but can I have a weapon that is simply a striking weapon? No +1 potency rune? Could I even go so far as to have a major striking Greataxe that lacks any other runes? (The answer presumably would apply to resilient armor runes as well, though I'd be interested if there's a divergence).
Inspired by this question – I almost instinctively corrected the questioner that a "+1 striking weapon is 100gp", but then realized that maybe they don't even need the +1 potency rune and therefore could get by with just the striking rune.
Best Answer
Yes, you can
From rune rules we get the distinction between fundamental runes and property runes
Here we get that the limitation to # of runes is limited to property runes, not fundamental runes
Finally, we get the magic word "typically" here, which is definitely not "always"
Looking at the fundamental runes rules we get that magical word "typically" again:
While the cost for upgrade cost shows only examples starting at +1, it once more expressly calls out typically, and even gives an example (though not the "no potency" example) of one where you might skip up the striking path:
Nowhere else do the rules runes list any limitations on fundamental runes. So you can have all the striking you want without any potency, though you wouldn't be able to add property runes until you had potency runes to allow for it.
To address the additional question, not only would the exact same logic apply to resilient runes, it would be far more likely to find broad applicability there. Not every character cares so much about armor class, whereas everyone cares about saving throws, so much so that previous editions came up with ways of letting you stack +resistance to saving throws on top of other items without penalty.