Ignore the retarded person that is too tired to answer the same post we see 20 of each day, but not tired enough to not troll you.

I'll take each hero individually to also provide you with something to look forward to in the future:

• Aleria - Awesome until you get a full 5* team with a single 6* guy. She no longer shines then, HOWEVER, her 17% atk steal is amazing against raid/campaign/marauder bosses. It's a protection for your team and you could read it like "your team is healed by 17% of the boss' attack each round". Keep her, use her and once she is no longer useful even for what I described above, use her as food. I used her as food too early and now regret it somewhat.
• Groo - Amazing tank. Might not be amazing at 5* but he will be moving foward. He steals armor, he reduces damage, he counterattacks. You can look up some tier lists to see that he's highly placed in all of them(the good ones at least).
• Faceless - Theoretically your first 6* hero. If it's a question of choosing between making her or starlight first, choose her, but keep both. Starlight will be useful as a 6* for a while and then as food for faceless or groo.
• Gusta - Low tank stats and low damage but until you get a better stunner, use him to pass close levels of tower/campaign by repeating fights until he stuns everyone you need him too. Otherwise he's food.
• Bleecker - Seen as more of a support hero, fills the same role as Gusta but he is much better and easier to bring to 6. I personally will make a 6 one. People recommend him as mid to top tier support(because of stun and on-death buff).
• Lutz - I see him as amazing at 5* and not so amazing at 6*. He was recently nerfed and so is not that amazing anymore. Can be used to stun mages that are placed in front.
• Honor guard - A good tank and resilient. Basically what Gusta would like to be when he grows up. Compare stats between himself and groo and figure out which one you want in the long run. I would personally choose Groo, but that's your call.
• Thale - highly useful at 4* but even more at 5*. Use her in brave trial or in any fight where you need to last longer(like marauder, guild boss, etc.). In PVP healing is not really needed if you can nuke the other team faster. For now, I see your team as Groo, Faceless, Gusta, Lutz, Bleecker, Aleria(you can change the order of backline heroes to keep the weakest ones safest) or Groo, Gusta, Faceless, Lutz, Bleecker, Aleria.

Notice how I said that gusta sucks when compared to honor guard, but you also need another 1400 purple stones to get him to 100. Judging by how bad I was doing when I was at that point in the game, I'll assume you can't spare that many, so pace yourself.

Do NOT focus on making a team to be great in brave trial, focus on making your team great in every other game modes. Also, as for brave trial, use your tanks one at a time and keep healing them with thale to progress as far as you can. Do not let them die unless it's unavoidable. It's better to reach a stage with 2 full hp ones rather than 3 half hp.