Jaimers, the magic library is ESSENTIAL.
I am at the end of the plus disk and skill levels let me pwn foes I should be level 800+ or so to pwn, but I was only level 370-ish for Reimu. Me having insane Skill Levels made up for more then 400 actually levels :V At my point, if I give Patchy about 100 Skill levels in DEF, she gains like 5000-6000 DEF, not much DEF compared to chars like Meiling, but every point helps keep Patchy alive
Skill points are Infinate as well Jaimers, if you don't want to spend cause you think the game put a limit on how many you can spend, then don't worry. You can spend as you please and their is no penalty, the worst that could happen is that you might invest in a chars useless/not needed stat, like Remi's MAG or Patchy's ATK, that or you might run low on Skill Points, but you can always get more.
Edit:
BTW mystic, wtf is your skill levels so high, did you cheat to raise them? or did you just grind over and over and for some reason chose NOT to level up regular-style
I used cheat engine to get tons of skill points... I kinda regret doing so but I was at a point that was "I can either spend a lot of time grinding my butt off and probly add like 10 more hours to my file, or I can use cheat engine to give myself like 50 levels and a lot of skill points... *after about 15 minutes of considering and 3 deaths to
* Thats it! Cheat engine time" and thus, I gave myself roughly 50-60 levels, like 35 Gold Cloth and I think... 200 Million Skp... a 200M that due to me going rambo, I refilled whenever it got low. I ended up boosting most char that I use to about Lv 260+ in Elemental Affinity's, and the upper hundreds in stats.
Say what you will about me, but I was tired of the Disgaea-like grind-wall with no Disgaea-like grind method. I only used cheat engine when I lost numerous times to a certain boss that I spoiler-marked, I beat the game fair-and-square, without cheat engine.