You will want to check out EQ traders corner for more info - like the calculator.
Basically though -
-> when you succeed, you have a greater chance of getting a skill up then when you fail (this was per a Dev during the Las Vegas Fan Faire)
-> As the item gets harder to make, your chances of getting a skill up are much slimer (you will want to use the calculator for this - but for example - going from level 0 - 21, you have like a 80% chance of skill up. Going from 199 - 220, you only have a 5% chance of skill up on a success, but only a 2.5% chance on failure.)
-> The closer your skill to the items trival, the more likely you will succeed (this is a DUH moment, but when you figure in that you have a better chance of getting skill ups when you succeed rather then when you fail - it becomes obvious your not better off to do harder combines)
-> With items - your highest skill can ever be is 252.
Just yesterday I reached GM Brewing with my Shaman - it took over 900 combines of Minotuar's Hero's brew to get from brewing 193 to brewing 248. This was with me having 233 Wis and a Geerlok Brewing Device (which is +5% to skill). It took 80 combines to get from 248 to 249 off Kaladim Constitutionals, then another 55 combines to get from 249 - 250 of Sec Champagne
Just to see your results, I put your info into the Calculator
and got that you have a 63.5 % chance of success, with a 5% chance of skill up on a success and a 2.55% chance of skill up on a failure.
you may want to invest in a geerlok for brewing - the 5% will add 10% to your chance of success - meaning you'll more often hit that 5% chance. Doing the math - increasing your INT further won't really help your chance of skill up on successes (at that point in the skill - your capped at 5%)
So I would suggest buying a geerlok - which will help you succeed a bit more - and hope for the best
It is very mind numbing I know.