Honestly, you'll be fine. I beat the game at level 69, and I bought practically all the apps I needed. There are items that give you bonus 10 points as well, though they are few and far between.
Again, just focus on the important stuff
- Demon Skill+
- MC Skill+
- Compendium Discount (only useful if you fuse a lot)
- Skill Augment (random skills more often on level up, very useful)
- A few stock for some spare demons to fuse and capture
- MP Recovery (save this for last, but its super useful when handling small wimp groups)
- Demon Negotiation (removes garbled text)
All you unlock when you beat the game is "Extreme" difficulty, and the chance to do NG+ -- maybe some bonus bosses and such on NG+, I dont know