Gaza isn't occupied for almost 20 years. The only issue Gaza had is no freedom of air and maritime space, and no freedom of travel outside of Gaza, all those authority is oversee by Israel. What hamas can do is, with the help of Qatar and other islamic world that understand their issue, secure a diplomatic ties with Egypt and open up the rafah crossing, secure funding in the mean of loan and build facilities(electricity, water) to become more independent from Israel, have a force strong enough to prevent Israel attack, and stop lobbing rocket at Israel.

Of course, this will face strong objection from Netanyahu because he's a bitch, but at least then it's very clear the issue lies with Israel, not Gaza. You gotta show the world you're willing to build up, and willing to respect the Greenline that you say you want Israel to respect.

This, of course, is oversimplifying the politics between Hamas vs Fatah and Hamas vs the west, and the hatred that's swelling up for the last few decades or so, but at least it's a good base to stand on.