Suggestions?

I want to start a new game but I want a challenge
Any suggestions?
Not solo's cause they're not that difficult

Don't use ability spheres.
Don't use power spheres.
Don't use the sphere grid at all.

Any of those 3 could be challenging

No sphere grid is a fun one... I've got as far as the 2nd seymour fight, but I don't think I can go any further... (forgot to get some items beforehand)

It's all about Mix :D