Where should I start?

I know this is a relative question but I recently started playing ATM for the first time, and I still have knowledge of the mods like industrialcraft used back in 1.5.2 (I'm a dinosaur), but this is way too much for me.

Quests are the best thing that could have happened to Minecraft, but what do you think are the best mods or the best quest groups to get started with mods?

Thanks!!