Unfortunately you're in the wrong forum for picture-based (presumably event-based) systems.
You're looking for
RMXP Troubleshooting.
Also, to do a sphere grid system you might want to figure out exactly how you need it to work.
If you expect it to be the same as in Final Fantasy X, where everything glows and you can see every other character's trail...
...Good luck.
The first thing you should figure out is how you're going to make the enemies you fight give each character "AP" to level up.
Alternatively, you could use EXP and set the game so your character never levels up in the default way,
but when the character reaches a set amount of EXP you add (+) 1 to a variable for the character's level.
After designing your sphere grid you would have to make each node check to see if the currently selected character
had a level of 1 or more (greater than or equal to), then check for the sphere you selected (greater than or equal to),
and finally add whatever attribute you select, then subtract (-) 1 from the character's level variable
and subtract (-) 1 from the selected sphere.
The rest is pretty much graphical.
I could make one out of a map and events, but if you wan a picture-based one, I can't do much.
It would simply get too confusing to have to work with so many pictures and placement.
I'm sure I would end up making it full of bugs if I tried a picture-based one.
Anyway, good luck on your sphere grid!
Hopefully someone else here will be more skilled than me with pictures.