I’m feeding the baby, but I’ll chip in with a bit.
Here’s some great FREE rosters that players have built.
Don’t rush to 5*. They takes millions in food and thousands of feeder heroes. Your first two 4* will be useful for months to come
https://forum.smallgiantgames.com/t/who-has-the-best-f2p-roster-in-the-world/68800/8
Here’s some great training alliances
https://forum.smallgiantgames.com/t/teaching-alliances/39771
I obviously recommend the Guardians family training alliance, Guardians Academy, but there are lots to choose from.
Greymane - Ishtaak - Rigard - Hawkmoon - Bane
For starters at a glance. Then kashrek in the middle when he’s levelled up.