Once you finish your first round in the jungle, you should be about level 4 or 5 with enough gold for MOST of Wriggles. This is without ganking. Mid lane will be level 6ish by then, along with solo top.
so you're a little behind at this point, which would be normal.
but consider, after you're leashed on blue (for example). you're level 2 while everyone else is 1. Go gank right then.
wait for everyone to get in lane, I like hitting top lane, but that's just what i'm used to.
gank hard and quick, don't dive. even if they burn a flash it's a win.
then look for another gank around lv 4 after you get red buff before you re-clear wraiths and wolves or double golems. if a lane is getting too sassy and pushing up on your tower, cut them down.
if you are successful on even one of these ganks you are at wriggles when you're done with your first round of the jungle. snowball from there.
Or invade at level 2/3. if you start blue, go hit them when they get to their red. 300g in your pocket.
after your first round, just a few more camps and maybe cover someone's lane while they back. and you're at 6. ult is up and bot lane is exposed. if you're quick you will almost always hit 6 before bot lane. hit them and keep them down. get a kill or 2 out of it.
The way to get your jungler rolling is to find a balance between ganking and farming. too much of either one will leave you crippled in the mid game.
after about level 11 when the team phase starts, I will always pull about 2-4 levels ahead of everyone. just cut your jungle down whenever you're passing by, grab buffs unless someone else needs them. clear lanes if minion waves build up. (I play nocturne, so I can get back in the fight pretty fast)
With that xp is also a lot of gold. I also solo dragon at 10, keep it on a timer so you're back in there grabbing it whenever it pops. Don't be afraid to invade, take their big wraith or wolf, it adds up fast and keeps their jungle crippled.
if your jungle is clear, look for ganks. free, easy money.
if all your lanes are pushed, then you'll have a little dry spell between level 6-8. but once the laning phase is over you're free to pick up cash from minions of jungle at your leisure.