This is rather a long subject that the admin has posted.
Its an amalgamation of all the information that can be found in the forge.
If you cannot find it there, it probably means you cannot forge the items , so except for the purpose of long term planning, you probably will not need to worry about it till you can.
Its supposedly better to wait till all the items you are using to forge are legendary, then you will get the best bonuses.
However, if you look at the big players hero and shaman ( at the times they are visible) or many others players as well, you will see they might have a mixture of equiment at different levels.
That is they forge low and then upgrade.
The drawback of this is, if you dismantle an item that consisted of four pieces you will only get one of them back.so you loose a fair amount of stock this way.
This may be of low concern if you are spending a lot of cash or gold on energy packs.
So the choice is yours,
To forge and upgrade, or wait till you can afford the top piece, or maybe settle for something in the middle and stick there ,until you can more easily afford to upgrade.
If you consult the forge and study the things that can be made there,(even if you cant buid them) you will be able to see what effect the quality of the starting materials has on the final piece, and the actual bonuses the different levels of equipment give.
You may have seen this already and worked it out for yourself, but if you can forge all 6 pieces of equipment with usual items, the result can be a total bonus which is more than just a single legendary piece.
