The trouble with your Gungan Jedi is the fact that until after the Battle of Naboo, Gungans were not really a part of galactic society. This also means that there were (in all likelyhood) no gungan Jedi before then.
Now, the Jedi normally take children at a very young age to be trained. Say your gungan was discovered and tested immediately after Episode I took place. Poor Toga now has about 12 years to become a 10th level Jedi Master, before Episode III takes place and he dies along with all the other Jedi.
That means he's a Jedi Master at the age of 15 or so. But remember, Anakin was supposedly too old to recieve training at the age of 9, and Obi-wan became a Jedi Knight at the age of 25.