After some consideration, I think the luck potion is the best play. Here's why:
1) There are proven methods that already exist for increasing skill. So I could use those to improve my strategy and execution. And if I were to do so, I would likely quickly pass the 1% skill edge I gained from the potion. As there is no proven means to work on my luck and run 1% better than expectation, it will have a more permanent impact on my results.
2) There are spots in which I already know the correct play, and a skill edge increase does not make one any better in such spots. A luck edge has impact in every spot where cards need to run out, and at a broader level the type of spots that emerge could be 1% more favorable as well. So in this sense the luck edge will have broader reach, and therefore more impact.