@CF_Jedi1234
Luke is useless, and you have far better options even at low levels. Lando or GS are far far better options to farm from low level Cantina. Luke is a collector's item, and even in a full rebel team he is underwhelming. He's slow, vulnerable and his damage is nothing special. His stun requires a crit, and is on a special, and thus not reliable at all. GS is all around a better toon, and Lando is useful in too many parts of the game not to farm him. The only reason to farm Luke is because it's Luke Skywalker and it's a crying shame we don't have Bespin Luke, or RotJ Luke, who might actually be good. Oh, and Luke was the guy I unlocked as my free toon, so I know that even at low levels he's not that hot (and I even farmed Leia first from arena so they'd work together).
In addition, your farming advice is Arena store heavy. You can't get Leia, Ackbar, STHan and Sidious, let alone Asajj and Greedo as well. Focus on one of them (STHan, imho, as detailed above, but Sid is a decent option if you like dark side: high damage, good leader). Asajj and Greedo are novelty toons. They *can* work in certain specific team comps, but are definitely not all around useful. I'd argue Cassian is a better farm than either of them, not to mention the droids.
I also feel the Lumi advice for GW is a bit outdated. I followed the guides that advised Lumi first, and wish I had farmed Phasma instead. She's definitely not a bad option, and helps a lot in GW (which is a very important aspect of the game when you're starting: you really want to be completing them. If you're losing out on more than 1 in about 5, you need to focus on toons that help you more with GW, and ideally your miss rate on GW is once in a blue moon). Phasma is a good GW leader. She's also a decent low-level arena leader, and useful later in raids. Lumi is primarily useful in GW (although her AB does give her some clutch utility in low-level arena). And, imho, if you're not working on STHan from Arena shipments, you should get K2SO from GW: he's a beefy, reliable tank. More easy to nullify than STHan and his utility drops off later in the game (same as Lumi), but he has one big advantage, which is that he's mostly immune to AB, so if you run into problems with fast ability blockers (Boba) nullifying your tank, K2 is a decent work-around. I personally unlocked RG from bronziums very early, and used him until level 70ish. He was fantastic, but depends on luck to get from Bronziums, and(or) very dedicated hard node farming to star up. K2 is a good alternative, and daze is a very useful debuff.
From Cantina, Poe, 5s, QGJ and Boba are all good toons to focus on. I think Boba is best, because of a general lack of Dark Side toons early on for storymode and the extreme importance of credit heist (my first cantina farm was Daka, and she was even in my arena team for a while, but I would not recommend that route, because she's obsolete quite quickly). If going full rebel, Bistan is a pretty good addition. He's reasonably fast, hits decently hard, and has reasonable TM manipulation. I woulnd't call him top tier, but he's definitely more useful than Luke.