Hearthstone Battlegrounds is the new auto-battler mode available in Hearthstones Brawl mode. The game itself has many elements, both random and not, that makes every match unique in its own way.
While it is difficult to focus on the same particular strategy every game, there are some things you can do to increase your chances of winning. Combining and upgrading minions is one of the most basic things you will need to learn how to do.
How to Upgrade Minions in Hearthstone Battlegrounds
Combining three of the same minions will reward you with a more powerful version of that minion. Minions will always automatically be upgraded the moment you purchase your 3rd copy of the card. The new upgraded minion keeps all buffs from the first two minions.
After combining minions, you will need to decide when to play that new minion. Playing the new minion will reward you a card that allows you to discover a higher tier minion card, which is based on your current Tavern Tier. It might be a good idea to hold off until your tavern is a higher tier to use these cards.
Minions can only be upgraded once, so there is no upgrading past the initial three minion combination. Once minions are upgraded, any effects on the card like deathrattle or battlecry effects are increased.