Easy Mode

L2 medicine
L2 Science
L2 engineering
L2 Farming
L2 Culture
L2 Exploration

Medium Mode

L2 Science
L2 Medicine
L2 Farming
L2 Culture
L2 engineering
L2 Exploration

Hard Mode

L2 Science
L2 Farming
L2 Engineering
L2 Medicine
L2 Culture
L2 Exploration

My last is Exploration because its not very dependent and only some puzzles can do