What's your arena squad? How many Cantina energy refills can you do daily?
With your stuff I'd say run a Phasma Leader with Sid, Luke, Lumi and Daka. Sid is a better leader on on crit, high dps comps and apart from Luke, you don't have it. Max out those ASAP.
I'd say finish getting Luke to 7* in cantina battles. Then go for Kylo and max him, until you can farm Dooku at level 69.
Daka is a solid all around performer, Id say keep farming her to 7*.
If you go chasing Poe, he'll probably be nerfed by the time you ever get him into the field. AND, you need him at gear VIII to make him turn 7 (are you prepared for that?) if he isn't turn 7, don't bother, the dynamic changes the meta if he isn't going first and you'll have wasted your efforts and lost opportunity costs. Poe only works (for now) in high dps burst damage squads, you don't have it, adding Poe to your squad is a mistake.
QGJ is an option but you'll be again behind the curve on him if you don't already have him unlocked and you'll be left with a bunch of weak geared, half promoted 4*/5* mediocre toons by the time the next meta is figured out by the whales with the new toons. You probably can't compete with what they spend so why chase them?
You know what the difference between 1st and 51-100 is?
400 crystals, 275 arena tokens and 25K+ credits, that's what!
It's a cantina energy refill and 4x LS/DS energy refills on top of your natural recharge plus 5 extra shards every other day.
Focus on making your Arena squad as strong as it can be as soon as you can.
That means making the most out of what you've got, because the tokens and crystals you can earn by being consistently top 5, accelerates everything else by giving you more arena tokens but more importantly, the crystals for energy refills for farming crucial gear and hard node shards for less easily farmed toons like Ewok Elder, Resistance Trooper or FOTP (who will get fixed like Leia and won't be so OP) to break free of cookie cutter builds and leverage your oddball toons you may pick up in a lucky Bronzium drop (like I'm doing with Lobot whom I'm building a droid team around as a side project for GW and eventually, Arena).
I'm in a hard launch server, we'll all hit level 70 in the next day or two, and I'm consistently top 5 (2nd yesterday, 1st the day before, 4th the day before that).
I'm running a Phasma led Sid, Lumi, Daka and Kylo squad. I'm never out of the top 10. It can be done on very modest spending or even F2P.
Don't worry about chasing the flavour of the month, stick with your solid core and groom replacements one at a time and try to stay away from one trick ponies, opt instead for the more versatile toons (like Kylo) until you have a rock solid 7* squad, are succeeding consistently in Arena, then branch out.
By the time you get the latest "must have" toon like Bariss or Leia were, it'll have been nerfed into the ground (Bariss), fixed (Leia) or rebalanced and no longer the OP character you were after.
It's a mugs game, let the whales use the hard cash to learn the hard lessons and you can learn from their mistakes but don't mimic them if you aren't prepared to spend like they do.