I think I used 9ga 3/4" flattened expanded on my previous tractor. Very sturdy and small enough to keep sticks out but you can still see through it. This has yet to bubble up to the top of the priority list on the current tractor...Probably until it is too late!
When I bent my just over a year old tractor that is when improving the grill guard moved up my list. I used my last tractor with no guard at all for ten years with no problems. By a new tractor and I bend the hood, grill mesh and have the head lights aimed at the sky using the grapple.
Do not wait too long.