My attitude, and that of many other Buddhist teachers, is that ...
If there are future lives, heavens and hells ... live this life here and now, seek not to do harm, seek not to build "heavens" and "hells" in this world ... let what happens after "death" take care of itself.
And if there are no future lives, no heavens or hells ... live this life here and now, seek not to do harm, seek not to build "heavens" and "hells" in this world ... let what happens after "death" take care of itself.
Thus I do not much care if, in the next life, that "gentle way, avoiding harm" will buy me a ticket to heaven and keep me out of hell ... but I know for a fact that it will go far to do so in this life, today, where I see people create all manner of "heavens and hells" for themselves and those around them by their harmful words, thoughts and acts in this life.
And if there is a "heaven and hell" in the next life, or other effects of Karma now ... well, my actions now have effects then too, and might be the ticket to heaven or good rebirth.
In other words, whatever the case ... today, now ... live in a gentle way, avoiding harm to self and others (not two, by the way) ... seeking to avoid harm now and in the future too.