I've found it insanely hard to brawl with more than 1 attribute, unless your ENTIRE strategy revolves around it. You can guess what attribute I use, but so far pyrus and subterra have the highest gs, soo… If multiple attributes works 4 u then great, if not, consider just using 1. 8)
Using one attribute has the plus of making it easy for your card choices to work with any of your bakugan. However, the flip side is that it allows your opponents cards to affect all of your bakugan as well. ( cards that refer to a certain attribute ).