Is donating half of the money saved for Hajj to the people of Gaza better than keeping it for Hajj, knowing that the amount is not enough for Hajj and three times that amount is needed?

Giving charity to the vulnerable Muslims is more paramount because Hajj is not obligatory due to insufficient funds, and fulfilling the condition for its obligation is not a duty. Furthermore, charity is a means of replenishment and increase, as Allah Almighty says: (And whatever thing you spend [in His cause] – He will compensate it; and He is the best of providers).