Don't start buying gluten-free products without first figuring out whether it's actually gluten or something else entirely. Bloating and gas have a thousand causes - lactose, fructose, too much fiber, eating too fast, even stress. If you jump straight to gluten-free products, you're throwing money away and he'll keep having the problem because that's not where the issue is.
The best thing would really be for him to get tested or have a doctor evaluate him, even if it's just a quick appointment. Celiac disease is specific, but there are other sensitivities. If it really is gluten, then it's worth it because these days there are decent brands and prices have dropped a lot - they used to cost double. But if it's something else, those products won't make any difference at all.
If you want to try without blowing your whole budget right away, start by cutting gluten at home - rice, potatoes, meat, fruit - instead of buying expensive substitutes. After a week or two, you'll see if it improves. Then, if you notice a change, invest in the supermarket products you actually need. But first, get a diagnosis.