I reccomend adding the other mod @
AlCapella recommend end as well - Bibliocraft.
Mods I recommend:
AE - GTech is hard and at time tedious, this will certainly help ease the pain in the later stages of the game
Bibliocraft - It's all about the looks
Project-Red - Just disable Rubies and Sapphires and have all the benefits of RP2
Galacticraft - It'd be nice to have a nice end goal to the GTech tree, just remove all of the duplicate machines and easy power generation
Mekanism - Take it or leave it. TBH I think it may not be fitting with the theme, but with the rebalancing of the recipes it could really have a place in the pack.
TiC - Just to annoy all of those stuck-in-their-ways GTech players
These are my ideas (the last one is not quite serious). If you do add these mods I recommend rebalancing the recipes with MineTweaker and remove duplicate power generators and machines (just keep factories, I love those things).