A regional campaign that treats the GCC as a single audience usually performs acceptably in one market and poorly in the other five. The countries share a language and very little else that matters to a marketing plan.
Competition is not evenly spread
The UAE, and Dubai in particular, is the most competitive search market in the Gulf. Broad commercial terms are expensive and the results are crowded, which pushes smaller businesses towards specific, high intent queries rather than head terms. Oman sits at the other end, where organic search is still reasonably winnable and a business that fixes its technical foundation early tends to hold position for a long time afterwards. Those two markets need different plans, which is why they get their own page for the UAE and a separate one for Oman.
The language default changes by country
Saudi Arabia is Arabic first by default, and keyword research that starts from an English list will miss most of the demand. The UAE is the opposite problem: you are often addressing an Arabic speaking local audience and an English speaking expatriate audience with the same budget, and they search using different terms for the same thing. Kuwait sits closer to Saudi Arabia in search behaviour. The Saudi Arabia page goes into that in more detail.
Cost per click is not comparable across borders
Bahrain has noticeably lower paid costs than the larger markets, which makes it a sensible place to test creative and offers before pushing them into Saudi Arabia or the UAE where the same mistakes cost considerably more. Qatar is concentrated, with a small number of competitors dominating most commercial results, so precision at query level matters more than volume of output. There is a page for Bahrain and one for Qatar covering each.
What to do with this
Pick the market that matters most commercially and build for it properly rather than building something generic for all six. Add the others once the first is working, adjusting the language default and the query strategy each time. Structure the campaigns so each country can be judged on its own cost per result, for the same reason you split platforms in an app campaign.
I work from Kuwait across all six markets, in Arabic and English. The Kuwait page covers the home market, and the technical and bilingual search side is on the SEO consulting page.