Instead of trying to make it more "jovial," you could use these options:
For a more intense level of joviality:
* More jovial: This is the basic comparative form, though it's not very common.
* Extremely jovial: This emphasizes the high level of joviality.
* Rhapsodically cheerful: This suggests a heightened level of exuberance and good spirits.
* Exuberantly happy: This highlights the energetic and joyful nature.
For the highest level of joviality:
* Most jovial: This is the basic superlative, but again, not very common.
* Unusually jovial: This emphasizes the uncommon level of cheerfulness.
* Blissfully happy: This conveys a sense of overwhelming joy and contentment.
* Overflowing with mirth: This describes someone bursting with laughter and good humor.
The best option will depend on the specific context and the desired nuance.