I don't think you need a tech tree to play tekkit, sure, it has a lot of mods, but after all, it's still minecraft, imagination and creativity is the key. The best thing to do would be watch tekkit tutorial videos, direwolf20's video is recommended. Then, you can check each mods' individual wikis, as it tells you what to do, some of them has a getting started guide.
Direwolf20's channel http://www.youtube.com/user/direwolf20
Must read wiki:
Industrial Craft http://wiki.industrial-craft.net/
BuildCraft http://minecraftbuildcraft.wikia.com/wiki/Minecraft_Buildcraft_Wiki
Equivlent exchange http://equivalentexchange.wikispaces.com/
Redpower http://equivalentexchange.wikispaces.com/