Save your Crates. Do not open common crates one by one. Save 100 Crates for a guaranteed Legendary drop.
The primary gameplay loop involves surviving "Days" (waves of enemies). Enemies will approach from both sides of your defensive structure. days+bygone+guide+new
Heroes provide the automated utility and damage needed to reach higher days. As a new player, you should look for heroes that offer "Crowd Control" (CC) rather than just raw damage. Save your Crates
skill at approximately 2x the level of your damage skills to maximize growth. days+bygone+guide+new