Use the "Skip" button to shorten the battle scenes. However, if you get defeated, go back and watch the entire battle to learn why you lost and adjust your strategy.
Heroes
When first starting, select the best heroes to build a strong team. As you progress into different expedition areas, replace slots with heroes that are better than your current stock. Stats are the best thing you can use to decide whether to include a particular hero to your team. However, as you progress and face difficult battles you also have to consider team combo and team work. Upgrade your formation to add slots for available heroes that you can include in your team.
Resources
When you have access to the mine at your main base, at about level 30, use it to get a list of mines. Some of them will be owned by other players. You can attack another player's mine and take their resources. You can also claim an empty mine and use it to earn silver over time.
Silver
Save silver to purchase equipment to enhance your heroes. Farm completed missions to earn silver.
Upgrades
Equipment upgrades and hero training is always less than 10,000 silver. Always spend silver until your heroes and equipment are capped. You should never run short on silver.