Collecting every shard you can is a big no-no in this game unless you're a whale. To be competitive you must focus on a few toons at a time. About toons you mention only Boba is a sure bet atm but he requires a lot of expensive gear. You can also focus on a faction rather than specific toons. Rebels, empire, jedis are good atm, nightsisters, jawas, tuskens, ewoks are not. You will need 5 scoundrels for the credit heist which brings lot of cash.
Right now I would start over if I were you, just to get a high rank from the very start in arena. Check the top ten prizes , it's worth it : use crystals to refresh energy twice a day, cantina energy once, rest to buy gear. You can find guides on forums, reddit, lordskunk.com, youtube. Get a swgoh.gg account and a nice guild asap. Or just play the way you like if you don't care for competition, and have fun.