You can always customize the way you level up your abilities depending on what your team needs or the weak point of the enemy team.If you are ahead you need to keep that going by ganking so i reccomend maxing your e.Now if you want to be more passive and become a farm king just max r or q or both of them depending your gamestyle and your build.Always remember to do the skill combo right,it makes a huge difference in-game.Good luck!