I'll say that you need to first get someone to 7 stars, then find a guild that's running heroic rancor (if you aren't in one already). Even as a new player, it's probably more advantageous to come in last in a heroic rancor than first in a lower tier. That lower level gear you can easily request from experienced guildmates.
Build a team around a synergy, which is often a faction. For example, Rebels work great under a Wedge lead (especially if you have Biggs; he's a quick GW farm, and his ship is great). Try to get a few damage dealers, a support (maybe for healing/cleansing/buffing/debuffing), and a tank (except in early LS/cantina battles, where tanks are still too weak and may end up costing you three stars). So with what you have, you might think about a squad like Wedge (L), Biggs, Fulcrum Ahsoka, Chirrut, and Old Ben. (Speaking of synergy, Fulcrum Ahsoka here benefits from the buffs that Biggs and Chirrut can give.)
Prioritize someone from each farming location and generally work on them until they're 7*. Who are you farming from the guild shop? Cantina nodes? Cantina shipments? Arena? GW? Hard nodes?
Like everyone, you need credits. You've got a lot of leveling to do, and your mods need leveling. Prioritize getting a scoundrel team strong enough to complete the highest level credit/droid heist available. A lot of scoundrels have almost no end-game value (Greedo, Zam, Chewie just aren't going to be viable long-term, as the game stands now), so try to eventually work on ones that will: Boba and StHan are good choices. Lando is good (but will compete with Wedge for farming). Captain Han Solo will become important when you do territory battles.
If you want to do well at raids, you'll probably need to keep working on Teebo, Jyn, Phasma/Fives, and TIE Fighter Pilot until you get to other options.
If you'd like legendary characters (GM Yoda, Palpatine, R2, BB-8, Thrawn, CLS), think about the teams you'll need for those. Some toons have more than one faction tag and can do double duty: Lando and StHan are scoundrels and rebels, so they help with credit heist and Palpatine (and StHan is needed for CLS); Phoenix Squadron are rebels, so they can get you both Thrawn and Palpatine).
If it would help to have a general idea of which toons have long-term viability and which are a waste of resources, AhnoldT101's ranking table will give you a good idea: https://hydra314.github.io/SWGOH_ranking_table/ranking_tables/rankingtable.html . But know that it favors versatile standalone toons that can fit anywhere. Some niche toons still have good value: Hoth Rebel Scout and Soldier are needed for TB; K2 can be good with Cassian or a RO squad; Jedi Consular is awful in battles but has a pretty good ship. But in general, you can get a feel for who is worth investing in and who isn't. (Bodhi, JKG, Zam, Greedo, Chewie, and IG100 are just bad toons right now. I wouldn't invest more in them.)
Farming guides abound, but make sure they're up to date.
Finally, though there's a lot of great advice around, if you just want to have fun, then farming who you like isn't the worst strategy as long as you have a few bases covered (a scoundrel squad, a rebel team, a rancor team, etc.). Many toons that are super good now or are required for something were once garbage (Boba, Kylo, Finn, Biggs, Barriss, etc.). And when they became good, everyone who already had them had the last laugh while the rest of us caught up. So if there's a character you love, go for it, and someday they just may well be good or necessary.
