I know this is a little late for the post since the weekend is almost over - but I will eventually have to post this anyways :/ Sorry if you guys didn't make it this week.
So, weekend dungeon. First thing first, remember to change your team back to the trio colors if your main is a Dark / Light team. It is a common mistake to forget that this dungeon does NOT have any dark and light gems.
There really isn't any special strategies in the higher levels except for either x4, x5 or x6.25 multiplier because the bosses are: (1) all three colors; in Expert/Adept level, (2) random of the one / two trio colors in Master Level. So let us analyse:
Novice / Adept Level (10 / 15 stamina):
I don't think anyone should have any trouble dealing with these two levels if your team consists of any x4, even x2, multipliers. Bosses are three color golems and they hit averagely 600 per 4 turns.
Expert Level (25 stamina):
x4 multiplier (pure color) is recommended instead of a mix of some random colors in the team or x2 of two colors.
Salamander HP 121650 ATK 3210 TURNS 3
Dragonette HP 151650 ATK 5910 TURNS 3
Sea Serpent HP 166650 ATK 5620 TURNS 4
Since Dragonette and Sea Serpent do high damage, your objective is to kill them first. That being said, your x4 team would be of advantage if you chose Wood since Wood deals 1x to Wood and 2x to Water. If you only have fire though, then your objective would be killing Salamander and Dragonette first, and try to handle Sea Serpent left alone providing that you have more than 5620 HP.
Master Level (30 Stamina):
A really tough one. Recommended team would definitely be x6.25 Wood or x4 Trio, ladder being way more risky.
Round 9 - Expert Level bosses - see above.
Round 10 - Random two of the three 4 Star Carbuncles (Red hits 9516, Blue hits 9821, and Green hits 10125; all TURNS 2)
As mentioned above, the damage are almost unbearable. And even if you bring -50% damage reduction dragons, you might not have guessed the right one due to randomization. That's why x6.25 multiplier is highly recommended + Echidna/Viper Orochi.
Luck is definitely involved in this too. For example, if you have x6.25 Dragons (I'm guessing the team will most likely be a majority of Wood Dragons) The boss stage might have randomised two Water Carbuncles and you will still be screwed. On the other hand, if you have a mixed of dragons, you might not any of the Carbuncle in 2 turns. To be on the safe side, any monsters with the skills that can delay the turns of these two Carbuncles are also highly recommended.
So what about the levels? Why go with the higher ones when the lower ones are so much easier? Well, the higher the level, the more coins you get from the treasure drops! (1000, 2000, 3000, 5000 from Novice, Adept, Expert and Master respectively)
Whenever you need some coins, weekend dungeon is the way to go. But think first before you can really handle Master Level; Expert Level is so much easier and its only 5 stamina less per run comparing to Master. You do not want to risk that 5 extra stamina for around 20,000 more coins if you would have beaten Expert Level easily.