I'll start by saying Tera is RNG while people are gonna come in and bash this by saying lower chance means it won't ever masterwork the difference between master enigmatic scroll's and common scrolls are only a 2.5% difference. Common enigmatic scrolls can be bought from the vendor these are only a 0.5% chance of masterworking an item but you are getting more chances to masterwork then using one master enigmatic scroll. Think about it like this it costs about 520 gold for a master enigmatic scroll that is one attempt at 3% chance of success for 500 gold you are getting 100 attempts at 0.5% chance. If it ends up costing you 800 or more common scrolls it's still more chances then if you got the same amount in master enigmatic scrolls.
We don't really know how Tera's RNG system works but one thing I know for sure it's a pretty dumb system which even with master enigmatic scrolls you can fail over 100 times and RNG from person to person seems to differ a lot but we most likely will never find out the exact RNG formula usually games use a time based system using UID (user identification) serial over attempting to put a max limit on scrolls this means for most of us even the unlucky ones you have a better chance burning massive amounts of common scrolls over a period of time to masterwork items over using a possibly massive amount of enigmatic scrolls.
The one reason I believe that the system used is most likely based on time was I've had two of my own guild members masterwork at the same time while using common scrolls but the difference in the scrolls they used was much different one used 40 scrolls the other used 450. My normal luck usually seems to be later at night and that's always when I end up master-working items. Not to mention all of my previous experience in the game development industry and older games with trying to figure out the RNG socketing systems or enchanting / upgrading where usually time based systems its the seemingly most random way for a game to make a system. That people can't just easily master because we have no idea the exact formula and because of the use of UID it differs for each person. Even if one person could figure out what's lucky for themselves everyone else will differ time wise because each person would be built with a separate lucky time so to speak.
So anyhow most people might complain that its time consuming to spam 300 to 1000+ common enigmatic scrolls since it would require 3000 clicks to do 1000 scrolls but if you don't feel like putting time into clicking you could do what i do and use a macro to do it. A macro allows you to record a certain click action and then repeat it multiple times. Even someone without skills can set up a macro for doing this. I was working on the same thing last night with a friends priest to masterwork her conjunct boots. And you can leave it running during the day or night while your away from keyboard. You can't get in trouble or anything for using a program like this all your doing is automating your common spamming. If you have a macro program you normally use go ahead and use that one but if your new to this macro thing you might want to try Axife Mouse Recorder they have a demo version which works fine I didn't notice limitations with it and its really easy for someone who has not set up a macro before all you do is hit record do the process of master-working with a common scroll then stop it and put in the number of times you want the program to repeat it which will depend on the number of scrolls used and it will keep doing it till all the scrolls are used up.
One thing to consider in the end is when K-Tera went free to play common enigmatic scrolls where removed from the vendor to force people to spend more money on enigmatic scrolls from random boxes and stop the use of master-working using common scrolls. If common scrolls had such a low chance that it was impossible to actually masterwork an item they wouldn't have removed it from K-Tera the fact we are lucky enough to still have them can save us a lot of money because you can masterwork using common scrolls then save the master enigmatic scrolls for the re-rolling.
If you've had success masterworking using common enigmatic scrolls feel free to comment about it in the section below. And if you just feel like raging about how you think this is stupid don't comment and just don't use common enigmatic scrolls. This is just meant for people that don't feel like wasting money on a only slightly higher chance. Some of the people I know who have actually succeeded:
Lulumia: used 100 MES scrolls first failed all of them used 650 common scrolls and Masterworked her regent staff.
My slayer: 5 scrolls rerolling a level 27 sword masterworked
Klau: 450 scrolls to masterwork chest
Sepheria: 850 scrolls to masterwork a chest
Jyu: 1350 scrolls to masterwork regent tip
Update: I wanted to share a screenshot of a conjunct chest I masterworked with common scrolls I left it running with 400 scrolls and it masterworked with 100 of them. People keep wondering as well if an item that's masterworked can revert to being unmasterworked the answer to that is no. Once an item is masterworked with common scrolls it completely stops rolling because a masterworked item requires master enigmatic scrolls to reroll it. Common scrolls are unusable on a masterworked item.