You're off to a good start!

On the fuel storage, blitz plastic cans suck ass, find good mil surplus cans. Invest in stabil fuel stabilizer and double dose the stored stuff. I just got done burning gas that was almost 3 years old that had been double dosed with stabil and it burned fine.

Instead of getting a bigger generator consider a solar backup system or just how to use what you've got, most of the time a small genny will work if you use it carefully.