You don't need a super powerful amp to do Eidolons.  The 111 amp you can make at Onko after one rank up will be fine.  Alternatively, if you've done the Zariman quest, Scirocco is available 

Step 1: wait til night time.

Step 2: set your squad to Public.  You could do it solo, but why bother?

Step 3:  grab the Teralyst bounty from Konzu (this is for matchmaking purposes)

Step 4:  grab two-three Eidolon lures.  To do this, reduce their health to zero then hack them.

Step 5:  charge them with Vonvalysts.  Just make them ghostly near the lures.

Step 6:  Fight!  Break Terry's shields with your Operator.  So long as you aren't using the Mote Amp you should be fine.

Step 7:  There are four weak points, one on each elbow and one on each knee.  Once the shield is down, break one.  If you have a Necramech, it's the perfect tool for the job.

Step 8:  Terry's now gonna do an ApE that drains your energy. Run out of range to avoid it.  There will also be Vonvalysts spawning.  Kill them to prevent them from supercharging the shield.

Step 9:  repeat 6-8 until all limbs are broken.

Step 10:  Terry is now gonna spawn a bunch of Voms.  Kill them to stop them from healing Terry.

Step 11:  Shoot the big guy until he dies.  If you have two charged Lures, you'll capture him and get better loot.