Don't start over, your roster is decent, you just need to focus on a core of characters instead of spreading the wealth.
Sid
Lumi
GS
RP
Poggle
That would make a decent arena team, and you are already fairly far along in their progress. Get those to 7*
Optionally, work on
QGJ
IG-86
Poe
Dooku
As F2P, all the toons listed are fairly easy to level and star up. Poggle doesn't necessarily need to be 7*, so if you want keep him at 5*, or go 6*, then switch to IG-86 for your GW tokens for an easy DPS toon to get to cap.
More specifically:
Use GW tokens on Lumi until 7*, then choose IG-86, RP or Poggle
Use arena tokens on Sid until 7*
Use Cantina tokens on QGJ or Poe
Farm GS in Cantina until 7*, then Dooku
Oh and I just noticed your toons are only level 62-64 even though you are level 70. That's probably the single biggest source of your problems. Get your top 5-8 toons to level 70 ASAP, don't bother levelling other toons until you have done that.
