To what degree was Vladek’s survival based on luck, and to what degree was his survival based on his considerable resourcefulness?

I'd say his resourcefulness added to his luck. Vladek spoke a variety of languages; English, Polish, German, and Yiddish. This knowledge helped contribute to his and Anja's survival in a few different situations. When they were captured for trying to escape to Hungary, Vladek assisted a man in writing letters to his family. The letters had to be written in German, and the man did not know how to speak German. In return, the man shared his food packages with Vladek. Thus, the man got his letters and Vladek wasn't hungry.

When he was in Auschwitz, Vladek taught his block supervisor by teaching him another language. Because of this, the supervisor protected him from being sent to the gas chambers.