If you are looking for the main bag, the size is probably the main factor you will need to consider. You need to keep in mind that your gear set is likely to grow, so you should get a bag big enough to account for that. Also, with a truly good bag, you will never have to sacrifice gear space for convenience.
Another important point to look at is durability. A full set of scuba equipment is heavy, so you will need a bag that is made from heavy-duty fabrics and will be able to handle the load. You will also want to check for reinforced stitching to make sure your bag will last.
A small but extremely important feature of every scuba bag is its zipper. A good dive bag should have corrosion-proof fasteners and hardware. Salt water can damage metal pretty quickly, so take a careful look at all the zippers, snaps, clips, and handles.
In addition to your main bag, you will probably want a few secondary bags, such as a lightweight mesh bag, a case for your mask, a padded bag for your regulator, or a dry bag.
If you are looking for a Diving Gear Bag to keep your Scuba, Snorkeling, or Freediving equipment organized, DIPNDIVE has a lot to offer. We carry Mesh Bags, Backpacks, Duffle Bags, Roller Gear Bags, Dry Bags, Lift Bags, and Watertight Cases to make your equipment transportation as efficient as possible.