Yes, make the opportunity difficult and the jutsu costly to learn because that makes it more unique and more rewarding.
Probably gives the penguin a better chance of living?
Just brainstorming here...
When you check out the shack, there is a chance you don't see Kakashi.
To get rid of actuallly making scroll items if there need be?
Instead of buying scrolls, you pay Kakashi to teach you a jutsu.
Instead of a projection of Kakashi, you train with Kakashi at his shop.
If these scrolls actually become items you activate, they can be destroyed!
The item is not perishable/one-time use. I hope I could resell them. <<
Seeing higher ranked scrolls are rare. Think something along the lines of mounts.
And/or you only see scrolls that match your current specialty, and having the corresponding specialty is needed/not needed for the training.
The shop would have the option, 'I see you have a affinity for _____(Element). I can teach/sell you these jutsus/scrolls."
I don't like the idea that I need a certain specialty to see/learn certain scrolls, but just a thought to make it harder.
But might be needed if you are to get into a real spar fight with Kakashi, read on...
After you buy it and are done training it with turns, you have to test it by using it.
I'm guessing Kakashi will tell you when you've learned the jutsu (Projection asks you to test it at Kakashi's shop).
Jutsu can't be used yet.
You test it by sparring with Kakashi. Could be a real fight so the chakra cost/specialty is required to test it.
I want this to cost chakra as well but maybe not a good idea, so no elaboration...
I'd prefer it to just tell the outcome. This could get evil...
Like the jutsu backfires and kills you.
It backfires but doesn't kill you, but instead disfigures you and you lose hp/charm/turns/etc.
The jutsu simply fails.
Kakashi accidentally kills you.
You pulled the jutsu off perfectly.
If it fails then you must wait until the next game day to test it again.
Test one jutsu a game day.
If you died, I guess you may resurrect and try again.
You keep on testing it until it works meaning you've mastered it.
You may choose to keep training it before testing it again. Maybe the chance to pull it off will increase?
An expanded structure for the shop would be needed besides just the jutsus for some of the ideas.
If no scroll, just add 'Which jutsu would you like to train?' option.
For the last idea, 'Ah, you've finished your training, which jutsu do want to test in a spar with me?'
Something like that.
I know I did not add percentages for the outcomes.
Not really sure about how you'd program that.
A little off topic, but the thought of making your own original jutsu came to mind when reading the thread Gyu pulled up, but I see that the idea has already been mentioned.