ModCraft II is a skyblock, it is simple and intuitive, not bad to start an experience of modded Minecraft.
It's a good modpack for a semi-RP server, ModCraft II contains some coins uncraftable to create a stable economic system.
Why Modcraft II ? Because I have already created a modpack named ModCraft and it's the suite of this adventure.
So, if you want an adventure on a single block of dirt *and a tree* this is a good modpack for you.
System requirement :
Minimum 2.5GB of RAM, and 3/3.5GB of RAM for the best performances
2GB of storage
And a lot of fun !