Piranas imo are the best deck for elo because of the pill manipulation. This makes hard reads for your opponent. They are just an all around deck because they are solid in a mono deck or even in a half. What more can you ask for from Piranas

Roots mixed with Piranas

Ghiest and Piranas

There is no best clan.
Roots, Bangers, Pussycats, Piranas, G.H.E.I.S.T., and Rescue are all the best clans, but there is no best clan.

GHEIST and Piranas
Ghiest have good 4 and 5 stars while Piranas have good 2 and 3 stars this alliance is the best for ELO

Skeelz are great as half decks, esp when lots of Roots and GHEIST are around.

Piranas are my favourite.

GHIEST and Skeelz are next in line for me.

All-Stars at times, too.

Taljion's Targe

Take this as a template and modify it to suit your taste. This is my absolute favourite deck in the game, but others prefer to substitute Selma or another 5* card. Some even prefer Kristin over Scubb (weirdos!).

Some of my favourite halves are:

Piranas:
Tyd 3*, Smokey Cr 3*, Tula 2*, Hawkins 2*
Tyd, 3*, Smokey Cr 3*, Ulrich 3*, Tula/Hawkins 2*

GHEIST:
Toro 4*, Bristone 3*, Leviatonn 3*, Arkn 2*

Skeelz:
Chiara 3*, Praxie 3*, Danae 3*, Redra 2*
Manfred 4*, Chiara 3*, Praxie 3*, Danae 3*

All-Stars:
Striker 4*, Marina 4*, Kang/Randy 3*, Robb 3*

IMO there's no best clan, just the top 3:
All Stars, Pussycats, Piranas (Power Manipulation, Damage Reduction, and Pill Manipulation)
these are supported by others such as Sentinels, Junkz or Sakrohm,
GG's!