This is not a full guide of how to find the best brand of airtrack, but it should give you an idea of some of the main points to look for.
Airtrack Mat Construction
A high-quality airtrack mat is made with very durable vinyl suitable for boat construction. These products will take a beating even from the lightest tumbler, and therefore have to be able to withstand severe pressure. Double Wall Fabric (DWF) is something to look for.
Check user reviews on Amazon, YouTube, and gymnastics forums to gauge the reputation of various manufacturers listing air tracks for sale before investing in an air track mat.
Air Track Prices
If you want an air track mat cheap, your best bet is to buy either a smaller mat, or a used one. Air track prices range from a couple of hundred dollars to several thousand, so you need to do your research. If you see a used air track for sale which seems to be a good deal, check the reviews for that manufacturer anyway just to be safe.
Size and weight
If you plan on using your air track mat in your yard and it is too heavy, you will tend to leave it outside where it will be exposed to the elements and get damaged. But if it is too small, it will limit what you can do. You want to strike a balance. You might be able to use a 20 cm thick track instead of a very bouncy 30 cm thick track, and use a shorter one, to save weight. Or perhaps the thinnest version, the 10 cm, will work best if you want the closest experience to the gym floor.