What is the minimum skill needed to cast Mark and Recall, say 10% of the time?

Well, about 35 mysticism works most of the time and probably around 25 would work after several tries. A 10% chance would probably run you of of magicka before working .

You can but potions for both at Nalcarya's.

Thanks!

When you reach 40 you will almost never fail. At 45-50 I think you got either 95% or 100% chance at mark/recall. Above 50 you will always succeed.

The chance to cast any spell successfully is:

1.25[ 2(magic skill) + Willpower/5 + Luck/10 - Cost][ 1 - 0.4(Full Fatigue - Actual Fatigue)/Full Fatigue]

The cost of Mark/Recall = 18
Assuming Willpower and Luck = 40 and that Actual Fatigue = Full Fatigue
Then:
Mysticism = 7 will give a 10% chance of success
Mysticism = 23 will give a 50% chance of success
Mysticism = 43 will give a 100 % chance of success

As seen above Fatigue could play a major roll. For example: If your actual fatigue was equal to zero, your Mysticism would have to be 70 (43/.6) in order to have 100% chance of success.

If your actual fatigue is larger than your full fatigue, does that increase your chances?

Yes