In my opinion, they do not need to invest heavily in the military and weapons, which would only increase tensions in the region. Instead, they simply need to reconsider their strategic relationships, especially their relationship with the United States. Do not become slaves or accomplices to the US in waging unnecessary wars in their region against their own brothers.
The US initiated the war for its own benefit, but now the Gulf states are bearing the consequences.
We know the people causing tension and military instability in the Gulf states (it's the USA, Israel and some of the Western allies). This is because the Gulf states are too weak and let the US build military bases all over them. Can Qatar claim that they are a sovereign state when they have US military bases littered over their lands? I don't think so.
They can't even speak up to condemn the US and Israel's acts of causing a war and committing war crimes against humanity. They are literary captives as we speak.
If they had a robust military system, there would be no need for US military bases in the Middle East.
The funny thing is, the US is causing havoc in countries that are thousands of miles away from its homeland while its citizens have peaceful sleeps without a worry of running around as refugees to avoid air raids. Imagine if China decided to set up military bases in South America or even, let's say, Canada.