Here are some tips to help you extend your grind and make it more efficient:
Team Management Strategies
When you begin the game, don't buy anything. Instead, save up for a Gold Booster Pack. It doesn't matter which gold character you get, they'll help you power-level the rest of your team and carry you through quite a few levels.
As your collection begins to build, start building different teams to drain energy levels together. Basic RPG and MMO rules apply here - you want a tank character (Superman, Doomsday, Solomon Grundy, Wonder Woman), your attack "DPS" (Damage Per Second) character (Batman, Bane, Joker, Black Adam), and a support character (Nightwing, Lex Luthor, The Flash).
Keep a variety of damage types on hand; I predominently use Batman, Black Adam, and Superman to keep a blend of physical/energy and short/long-range attacks. Mix and match as you see fit.
Don't buy support cards. You'll get plenty from booster packs; sell off duplicate cards.
When in battle, block a lot, and save up for your level 3 super move whenever possible.
Once you have three gold characters, max them out before buying anything else.
Energy Management Strategies
The easiest way to power-level is to only refresh your strongest gold character, rotating everyone else behind him/her.
Don't put more than one of your strongest characters in unless you have to. If you have three gold characters, grind at a level where each can solo, then pair them with your lowest level characters.
Battle Strategies Against...
These superfreaks block a lot and have a lot of health. Only attack when you're sure you can pull it off, and never lower your guard; these guys can end you with one shot if you're not careful. Let them attack first, and be weary if you've hit a string of more than 2 combos. If your strongest character gets them below 50% health prior to activating your level 3 super move, switch out a character in order to save your strongest super move to knock out a fresh opponent.
These two characters are notorious for draining your power. The best way to deal with them is to either tag out or switch characters immediately after your power bar hits its first level. If you're fast enough, you can use Flash and Harley Quinn to juggle them for a decent amount of time.
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Brian Penny is a former business analyst at Bank of America turned whistleblower and freelance writer. He's a frequent contributor to Huffington Post, Mainstreet, Lifehack, and HardcoreDroid and an affiliate of Manduka and Tazo. He documents his experiences working with Anonymous, practicing yoga, and fighting the banks on his blog.