How to Scroll?

For temporary weapons, you'd want to straight 60 all 7 slots.

For more permanent stuff, try and pass a 10 on first slot if it's easy to obtain. 30 if it's a rare item. After that do as many 30s as you dare and finish with 60s. If you fail 3-4 slots in a row without booming I would just finish it with 10s or NPC.

Don't use 70s on stuff you care about, 70s are pure evil.

As for what stats you need, it depends on the class.

 

well, the source code of maplestory is unknown, so we cant know if its a "pure" (computer based) luck, or it has to do something with like pity timers (like, if u fail 49 10%'s scrolls in a row there's a 100% chance the 50 will work)

some do dummy scrolling, which is scrolling 10/30/60/70% scrolls on bad items with useless scrolls to get the hang of it, some have success, some render it useless.

and it really depends on price of the scrolls. like, if u create a dex overall, u can go either 10%>70%>60% or 10%>30>60 or like any other way u see good.

my go for clean and easy obtainable items is 10%>30>60%. for harder to obtain its probably 30%>60%.

 

It pretty much is completely luck based, as in, all events are independent and that you are, for example, not guaranteed a success on the 10th try with a 10% scroll after failing 9 in a row. However you can still calculate probabilities for various scrolling outcomes, and try to determine whether it's worth it or not based on the scroll prices and probabilities.

Like previously mentioned, don't bother using expensive and risky scrolls (30%s) on temp items.
If you have an item that you "need", especially earlier in the game when mesos are scarce, play it safe and use non-dark scrolls.
If you have an underaverage item, you could try landing a 10% on it.
For lvl 100+ items, you could aim to add 20+ att on it. Like with 1 10% and 1 30%, or 2 30%s and then 5 70/60%s. Or at least 4 30%s if you're feeling lucky.

There's an old school scrolling probability reference you can check out.
http://www.basilmarket.com/General-Scrolling-Reference-Wiki-2915

You can gain a few insights from it, like how 70%s are actually quite useful when you use them in bulk amounts when trying to make a decent weapon.

Landing 5 60%s in a row is approx. 8% chance.
Landing 5 70%s in a row is approx. 17% chance.
Landing only one 60 or 70 is 1 in 1.67 vs 1 in 1.43 ordeal. But if you consider 5 in a row as an event itself, then it becomes 1 in 12.5 vs 1 in 5.9.
Not bad considering that the chance of destruction for each 70% is approx 1 in 6.7.

So for example, if you were trying to scroll a maple impaler, and you only had one, then you could play it safe and just do 7 60% scrolls.
But if you had 2 or 3, and you wanted one to be pretty good, rather than all of them end up average, you should probably take the risk by dropping 5 70% scrolls and 2 60%s on one of them.

You might also start thinking about different scrolling strategies. Like whether or not it'd be cheaper to scroll a 22+ stat bathrobe by using 4 30%s and then 60%s, vs a 10%, then 30% followed by a mixture of 70/60%s. (Just an example)

Some other quotes from the reference (prices are just examples):