In this page is the guide written by Josh which tackles on some tips and tricks on winning fights in Brave Frontier for iOs and Android devices.
When I first started out playing the game, the key to winning in the Arena was to build a mono element squad and make use of their 50% damage boost leader skill. This was good for a while but people seem to be shifting towards using Felneus or Duelmex as a leader and using other units that have either a fast BB refill rate or a high hit count.
Hit count is a frequently overlooked stat in this game. It's important because the higher your hit count, the more BC/HC is going to drop each turn. Combining high hitting units with Felneus' or Deulmex's leader skills (greatly increased the drop rate of BC) means that you're going to fill or almost fill your Brave Burst gauges on the first turn. If you can pop off a Brave Burst or two on the second turn, then the chances are that you're going to wipe out the opponent's entire squad during that turn.
One of the most effective squad's to use this method is using Felneus and 4 Gun Goddess Serin's. Gun Goddess Serin's normal attack has 14 hits, and her Brave Burst is a 16 hit AOE attack. I've fought a few players that use this squad and I almost always lose to them as they fill their BB gauge's so quickly.
If you're going to use a squad that relies on wiping the opponent out quickly with a Brave Burst, then it's most definitely worth leveling your units Brave Burst to BBLv 10. Increasing your unit's BBLv means that it's going to hit more damage and has a better chance of wiping your opponent's squad out.
If you don't have Felneus or Duelmex, you can still build an effective Arena squad. My second choice to Felneus and Duelmex would be using Gaia King Lugina as your leader. His leader skill gives your entire squad a 50% ATK and DEF boost for the first two turns. This doesn't stack with Muramasa's, so it's better to equip permanent stat boosting Spheres like Medulla Gem's and Sacred Jewel's. As his leader skill benefits your entire squad regardless of element, it's a good idea to just use your best units in a Lugina squad.
If you don't have Lugina either, then sticking to the original method of building a squad to utilize the +50% ATK leader skill is your best bet. This can either be a mono element squad or a rainbow squad that uses one of the rainbow leaders (Michele, Zelban, Lodin, Tiara etc).
When building mono element squad's, most people try to build either a Dark or a Light element squad because their only weakness is also their strength. The other four elements all have a vulnerability, while Light and Dark's weaknesses pretty much cancel one another out. That being said, there's nothing wrong with building a mono elemental team for one of the other elements like Fire or Water, just try to watch your opponents leader when entering the Arena as this will give you an idea of what the primary element for their squad is.
Regarding unit's typing, I'd always aim for units with either high HP or high ATK. This makes Anima, Breaker and Lord types the best in the Arena. Lord units stats raise evenly as you level, Anima's HP is increased while REC is decreased and Breaker's attack is increased while DEF is reduced.
During the early Arena ranks, Muramasa is probably the best Sphere to equip to your units. It gives a +50% ATK boost for the first two turns. As you progress through the ranks and get more Spheres, I'd recommend using Medulla Gem's, Sacred Jewel's or Angelic Foil's.