Characters not worth leveling?

I haven't leveled G. Soldier. I have a few one star characters sitting.

Out of the ones you listed, I'm using -

Chewbacca
Jedi Counselor (Healer)
Talia (Healer)

Royal Guard (don't have anything better and does give good Defense buff)
Snowtrooper (don't have anything better)
Used Ewok Scout some but stopped once I got a better option
Used Clone Sergeant some but stopped once I got a better option

Also, the number of Stars will greatly influence how good your character is as well.

tbh you'll need Jedi consular no matter what. obviously if you're spending money go ahead and try getting another healer. but if you're not, I'd advise levelling the consular up to get you past more levels.

I guess id just like to know overall which characters are worth investing in. Should i avoid devoting resources to 1 star characters?
Is there a tier list for characters?

Wow - I'm level 37 and still only have 5 Light and 4 Dark characters. But, they get the job done :)

The ones I see level RG GS JC Talia. There are others you can start farming . In lower levels I did chewie, JC, QJG with cantina, and Lumi when you get GW. Best heals is Bariss but you can't really farm her until you get at higher levels

RG is on most top tier Arena teams ATM. Auto taunt and reliable stun.
GS is also on most top Arena teams, hits HARD and easily farmable from low level.
JC is needed as another healer to go with Lumi until you get Bariss.
Talia is ok but not necessary. Heals are for light battles, pure damage for dark.
Full Ewok team has crazy turn manipulation.

If those are all your characters, you should be able to level them all. If those are your old characters that aren't leveled and you're asking which ones to level up id say leave FOS behind.
Edit: you can level them all until you get better ones