This should help you.
My first "dive bag" was bought at Wal-Mart. It wasn't fancy but I got a roller duffle bag for $35 or $40 bucks. I had cheap metal zippers that quickly went bad with a little salt water on them. THe fabric was cheap also and tore easily after only a few trips.....
So... then I broke down and got a real gear bag. I paid about $125 (+/-). It has heavy duty zippers and re-enforced seams and is just made about 100 times better. It also has an extendable handle like the new suit cases do so you can pull it easier through the airport. With the old bag, I had to hold onto a "soft handle" on the end of the bag and almost had to bend over a little to pull it.
There are several different brands to choose from and your choice might be different based on your individual needs. I chose to get one that didn't have many external pockets. For example, many have the external regulator pocket. I would never put a regulator in it because you are asking for it to get crushed, especially as checked airline luggage. Also very few divers will put their regulator in checked airline luggage.
Also don't get a bag that has "dive logos" all over it. It tells airline worker theives exactly what type of gear is in the bag, as opposed to regular clothes, etc.
Most divers carry-on their regulator, camera gear, and perhaps other items they are fond of such as their mask.
You might also want to throw in a large nylon or mesh duffle bag to use as a boat bag if you don't want to take your wheeled bag on the boat with you.
Hope this helps.
email if you have questions.
-mike