Post your roster. We should then be able to recommend some team compositions to you.

Save gems  for the 75mil and 100 mil damage to nightmare boss.  You might need to buy keys to do that damage in one day 

Oh yeah watch out for the upcoming ones where you have to ascend x affinity champ to 6* ascension. Those aren't retroactive. So if you're currently working on some new champs, it'd be a good idea to hold out with ascending their 6th star for the progress mission. 

As for the 20 dungeons, which ones are you having trouble with? Show us your roster like WatchdogCZ suggested.

share up pic of your champs we may be able to help you out once we know what you have available 

Scyl, Pedyma, High Khatun, Cagebreaker, Kael , Apothecary, Gala Longbraid, Azure, Lua, Sepulcher sentinel, Shatterbones, Captain temelia, Sandlashed survivor, Bellower, Marquis, Warmaiden, Avir the archmage, Elhain, Galek , ( will skip rest of uncommons and rares)

Shaman, Oathbound, Dark Elhain, Dark Athel, Stag knight, Defiled sinner, Knight errant, Mountain King, Ma Shallad, Senechal, Hellgazer, Delver, Hexia, Jizoh, Yaga, snorting thug, relickeeper, deathless, drake, torturehelm, bushi , cillian the garbage, 

a couple of other epics are vaulted of little worth. 

Thats currently what im working with.

I currently Roll on auto:

18 Ice golem (Pedyma, apothecary, kael, cagebreaker, scyl)

18 Dragon Lair ( same team) the dragons debuffs get hard to deal with here. and possibly need more damage to break his ability to move any higher. Need a way to wipe debuffs out, maybe  spirithost or sepulcher can swap in ?

14 Spider Den (same team) This ones just a prob for me, spiders a dick. 

15 Fire Knight ( same team) Cagebreaker has 4 hit on his 2nd skill, and so do kael. Apoth has 3 hit which helps too, otherwise still a tough fight. maybe ma shallad with open wounds will help.

This team currently has 225k power. Right now spider den is my toughest one and have a long way to go.

Any suggestions or swaps would be nice to know. 

I consider maybe building ma shalld next to possibly swap in kael, will give more survivability. Will potentially help for all battles except maybe not fire knight since it will still be very tough to remove his shield in time to apply open wounds. 

also use the same team for clan boss, probably going to insert ma shallad and mountain king there. 

The single attack of mountain king should be devastating on clan boss. And the leech should keep my men alive. 

Will be difficult also because pedyma is my attack down so i cant replace him. 

Apothecary is too useful to change out.

Kael has very strong poison damage

Cagebreaker is my def down. 

Scyl is my main healer + resurrect. 

Maybe id swap out Kael and Apothecary. 

Maybe mountain king hits harder than kael even with poison. 

And ma shallad will keep the speed up plus leeching life. 

Only practice will tell.