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If you go to this page and scroll down it will list the possible potion effects http://ftbwiki.org/Potion_Flask
It also list the different ingredients for potions
It was added after people suggested it for the pack. The reason that people suggested it was so you could replace tool parts. I think it may be lucky/unlucky (depending on how you look at it) that you got auto-repair 3 on all your tools.
If you're still unsure as to which magic mod to add. I would like to suggest Thaumcraft, in a way there is a lot "tech" involved (technical thinking that is :p ). If I remember correctly, there is add-on mods that may involve technology too.
With this idea in mind, maybe other materials (diamonds, iron and tinkers ingots) could be used for more expensive things...
I like the idea that certain things could be bought if they're tedious to gather materials for or are needed a lot.