episode feat....or how much crystal am i supposed to spend for ftp ?

so earlier this episode we had an episode feat that asked us to validate 3 era challenge feat.

 at that time, we had the luke challenge with 2 feat per level.

i managed to get the first level with 10 something (probably 16-17) luke and got 2 feat.

today we have the IG-90 era challenge and i was happy to check that episode with my luke now 23 and IG now 22.....

well this time there was only 1 feat per level, but no problem....i only needed 1 for the episode feat....or rather i needed only 1 more for the first episode feat.

and since i managed to validate the second level i now only need 1 more for the second epîsode feat.

So here is my question :

how much crystal do i need to spend to get to an acceptable level to validate the third level (lv 35 oppoment) before the era challenge expire ?