This is something I accidentally found out through trial and error. At first, I was just trying a lot of things, randomly, to get a feel of things. Then, with this one trick, I started getting more wins.
This trick doesn't give you extra damage or anything crazy. It does give you an advantage over others and that advantage is enough to get consecutive wins. I think I never lost while I used this but I am not 100% sure about that. What I can say with confidence though is if you use this hack, you will surely win more than you lose as long as you follow one rule.
Lineup:
The only rule I found out so far is the 26 mana rule. You can use this lineup for probably up to 28 but not any more than that. Any more and I cannot assure that you would win that battle.
Another rule is that I only used this with level 1 units. So, I am unsure if this would be as successful if you use it with higher leveled units.
This is the lineup I used for the battle.
Incessant Sage: Archon that gives +1 armor to all of your units. It's a strong archon if your enemies would not focus on magic attack.
Twice Yester Knight: This is the tank of my choice for this. It's not the best but it's the best the Foundation units have to offer. I tried the other ones and I just lost a lot so I think this one is the best for Life element.
Lady Amara / Vengeful Monk: I got Lady Amara so I used her more often and more successful. She doesn't have an ability but has better health and magic attack so more consistent damage. You can also use Vengeful Monk if you don't have Lady Amara but I am not sure if it's very successful. I won some for Vengeful Monk but I had some losses too unlike Lady Amara.
Sherringham Logger: Has good damage, health and armor against other Sneak using units. It also has Sneak which I think is good so you can diverse where the attack is coming from. It makes it hard for the enemy to counter you.
Battle 1:
https://splinterlands.com/battle/sl_19928aa9bfae00eb24b73948f3e558b6?ref=aiko2ne1
The enemy used a Fire element team. Fire element excels in speed because of their archon, Barthalamas. I don't think they have a good lineup of monsters though so I don't really use them that much. Their lineup for this battle have a mix of melee, range and magic but all of them comes to the front. With their back line unit not having any armor, unless they evade my attacks, they would likely lose this battle.
Battle 2:
https://splinterlands.com/battle/sl_600a2ab1559c16ad80b98674a9739201?ref=aiko2ne1
The enemy used Death for this lineup but mostly neutral units. Like I previously mentioned, Nim Guard Captain is a strong unit against magic attacks. While Lady Amara wasn't useful in this battle, Nim Guard Captain is still vulnerable to melee attacks. Their back row as well, Vengeful Monk, don't have armor. So, it's easy to see that he would die first in this scenario. With him dead and Nim Guard Captain losing in a battle of tanks, Lady Amara can safely dispatch of Spellmonger that can also give me the win on this one.
Battle 3:
https://splinterlands.com/battle/sl_fd263b1e66d55145cc24b68871d2921f?ref=aiko2ne1
I think this is one of the best effort the enemy had. Both their back line units can attack so they can fully utilize the field. The issue here is that my archon gives my units armor. Even with just 1 armor, that means 1 extra melee and range attack that my units can withstand. Since the enemy does not have magic attacks, I simply win in the difference of damage and armor with this build.
Battle 4:
https://splinterlands.com/battle/sl_73e6720c434089d8ccfcca3229702c05?ref=aiko2ne1
This is the last battle I found. The enemy used Earth Element with units that have melee and range attacks. Earth archon gives them better health but this lineup still lacks damage compared to mine. The Heal is a good ability but the unit lacks damage to outdo my tank. With a few shots at the back from Sherringham Logger, I gain advantage in numbers and quickly outdamaged the enemy lineup.
I would've liked to see some against Water Element but I haven't encountered one yet. I did found one but it's a higher mana and even with the win, I don't think it's a good example given the limit I added at the start.
Why I Think My Lineup Works:
The more important thing is the mix of damage and the limited mana in the battle. With just 26 mana, in Frontier Mode, I realized that you can only use around 3 units. The Water Element is still good but the attacks are less diverse. The magic attack units also usually have no armor or low health which means if the tank dies, you normally loses that battle. The other good option is Death. The issue with the Death units is that their attacks mostly come from the front. It's also not as strong and their strongest suit, the Nim Guard Captain acting as the tank, doesn't really work against melee attacks. If your enemy is Water, the Death Lineup would probably work. If not, there's a chance that they lose. The lineup I have can deal with all of the elements as long as you are in this very limited contained situation of 26 mana.