The only really "bad" 5* character is that furry boy. I got Encore as my random guaranteed 5* and she's really strong. Anyways, after you roll the first 50 on the starter banner, it turns into a new banner where you can pick a target. People are saying to roll for the little blonde healer girl if you care about meta. Sometime today (due to all the launch fuckups), they're giving out another 5* selector ticket, separate from the selector banner, so pick whoever you like. It's not like you can brick your account. I rolled that wind monk lady in the beta when I played, and liked her a lot. She's kinda like Venti+Zhongli mixed up into one character and then nerfed a bit. She has a shield, heals, and her ult groups up small enemies. While she's creating the shield, she also makes a big AoE dammage bubble which is great for mopping up groups of little enemies. She was my primary target when I started this time.
Best advice is level your Union level (Similar to Genhin's AR level) as fast as possible to start getting access to the Resin (forget this game's name for it, stamina basically) dump. If you don't know what to grind, I'd recommend the skillup/weapon ascension dungeon since it seems to be my bottleneck about 15 hours in, but until you get that unlocked, xp/money is always a safe dump and it's one of the first things you unlock. Also, after you have explored some regions, go talk to the girl near the north gate of the town with the black icon on the map. She rewards you stuff for exploration progress and the first thing you unlock is a chest finder utility. It's better than Genshin's compass because you can deploy 3 drones and they will permanently mark the chests in a big radius until you recover the drone. Makes some of the harder to find chests easy.