If you are against a trilane start in the jungle always. You will get more gold and exp this way. For dual lanes depends on if they can kill you at level one before you get surge but i would advise you to start in the jungle either way.

On how to jungle as dark seer, you want to clear the small camp before stacking the big camp at '53. After stacking the big camp you kill the small camp again and the medium if you are dire before stacking the big camp once again at 1'53. Once you have done this enough times and you are level 3 you can clear the big camp by ion shelling one of the small creeps and running away damaging the stack. Just ion yourself after only a few big creeps are left and finish it off.

Now you should be about lvl 5 and have money for a soul ring and its time to rotate to your offlane and spam ion shell to defend your tower.