When forging you should use a different types of minions for better results. If you use just one type of minion you will only boost one attribute. For example, a when forging a steel sword, if you put 100 brown minions to upgrade you will only increase damage, but if you use 50 brown and 50 red you can increase damage AND fire damage.
Skipping the First Troll
On Legendary, the first troll is very hard and consumes alot of minions. There's an easy way to completely skip him (Make sure you have 10 minions):
Head straight to the troll, and you'll get the cutscene of him getting ready to face you. After that, send all of your minions to open the gate where the crane is, and rush there (the troll will probably kill a few of your minions as they open the gate, but that's better than wasting 20 - 40 minions trying to kill him and also, if the troll is blocking the path, simple lead him away and head through the gate).
Once done, go to the crane and an autosave will occur. This is where the trick comes in: That autosave assumes you defeated the troll as you went further than you were suppose to, therefore, simply leave the area and come back, you'll find the troll has vanished as the game thinks he has been defeated.
Stock up on brown minion lives
A good place to get lives for brown minions is the first area(take left road). If you go after you have unlocked the first forge you can find about 40 sheepies (in other words 40 lives) just kill the sheepies (they are extremely easy) and you can get the lives.