The Aberstonium Modpack is a great modpack for adding more progression and exploration elements into Minecraft.
This modpack mainly focuses on adding things to the "end-game" of Minecraft. So it's not until you defeat the ender dragon will you start to get much of the new content. The game will feel very vanilla like when starting off and progressively get more different. It's a great modpack for those who haven't played a lot of or any modded minecraft before. However, it also offers something different than what traditional modded minecraft players are used to. There is also one of my own mods here as well to better help with progression and it is available separately as well.
In the modpack you can expect to find new biomes, dimensions, weapons, structures and more. The modpack should allow you to keep coming back to your minecraft world and always being able to find something to do.