I just want to add that Prospector Zeke's quests are very helpful because you get a training point for each one. Training points greatly help you when you want to get certain shields or boosts, especially the sun school boosts in Celestia and Zafaria.
I remember when I first joined I thought I had to do all of the quests. God, the worlds of the spiral seemed so long. Keep in mind that nearly every character you meet will give you a side quest, so honestly that's like two storylines. You could get some rare items and maybe some extra XP, but the worlds go by much quicker if you don't do them. I finished Krokotopia in a day and got to Big Ben in Marleybone in only two days.