Well it really depends on your particular circumstances. What level do you have each of those characters?
Assuming all three are 150+, it then depends on which class you wish to power level and your level of resources.
Ranger- Medium amount of resources (pots and idols), light-heal always helpful, bolas is very helpful if youre leveling a ranged alt (i.e. ranger, druid, or mage) and mildly helpful for surviving close calls with melee classes, decent dps helps regardless of alt class.
Warrior- Most resources; go dps with taunt/warcry built in (obviously keep enough hp to avoid problems), great balance to help all classes
Druid- Least resources; bark, embrace, heal, remainder in dps; great for all classes, but expect slightly less xp per lix
Enjoy the little things in life...
One day you'll look back and realize they were the big things.