Farseer how many powers?

I am planing on running a farseer on a jetbike with my beastbike to give them re-rolls to hit. I am wondering how mutch more I should buy for him? Warp charge 2 and another power or more powers?

Nope,if all you want is prescience, then just go 1 power... And runes of warding.

Precience is the main thing you want. If you have the points, might give him a second power as some of the other ones are quite useful as well (a 4++ save to one unit is always nice, and the one thta lets you reroll reserves is veyr useful if you use multiple flyers or WWP).

It depends...what else are you running in terms of Eldar allies?

Some of the points might be off. I am doing it by memmory. My default list looks like this, but I might need to ditch the exspensive plane and get something else. I have a nicely converted bastion with a lot of battle damadge, as well as 3 jetbikes with a melta lance. Both who I would like to include, but I guess you can not have everything. I mighty also be sinking way way to many points into the beastpack at the moment. I could always reduce it a bit as DE should be all about MSU and around 540 points is invested in it at the moment. The reason to include eldars in the army is for psykick defence and cheap scoring units. I find my warriors tend to die a LOTT.

Roughly estemate for a 1750 all commers list:

Baron Satonyx 105

4 Blasterborn
Venom, Venom Cannon 177
4 Blasterborn
Venom, Venom Cannon 177

5 Kabalite Warriors, Blaster
Venom, Venom Cannon 125
10 Kabalite Warriors, Venom Cannon
Raider, Splinter Rack 175

5 Beastmasters, 15 Khymera, 4 Razorwing Flocks 300

Ravager 105
Ravager 105
Razorwing jetfighter, Venom Cannon, Flickerfield 165

Allies:
Farseer 140 Jetbike Bike, Rune of witnessing, rune of warding, one psykick power 140
3 Eldar Bikes, Shuriken Cannon 76
5 Rangers 95

I think I'd go with what has previously been suggested. If you were fielding a larger contingent of CW Eldar I'd suggest taking an extra psychic power from the Eldar codex (usually doom) but as it stands it seems you are taking the Farseer to buff your DE units. However if you could find the points I think a unit of Striking Scorpions would compliment your beast units nicely. In which case a fortune/doom seer would benefit the Scorps nicely. The Scorps are expensive, but their 3+ armor, infiltrating skills and high number of str 4 attacks are pretty nice especially considering the toll overwatch can take. I actually think Striking Scorpions would fit really nicely into most DE lists, especially considering they could run a disordered charge against multiple units, absorb the overwatch and allow units like beasts and wyches to come in and mop up.

you cant take Eldar psychic powers and rulebook powers. Its either one or the other...

Just stick to 1 power, the only bonus for getting two is you "might" get something to help you, and the increase to the deny the wych roll for being Level 2.... but that is what rune of warding is for.