Perhaps give a bit more information about your situation, for an example are you on a budget, which cards do you already have that is strong and stuff like that.
Since your level 20 atm i presume your probably on a budget so ill try to suggest something cheap.
Roots half deck 11 stars / 13 stars
The deck suggested here should be fine for a starter ELO deck and if you don't buy the most expensive cards you can get the deck for under 5k clintz. It should be able to get you beyond 1200 in ELO and 1300 if you got the skills and time.
Use Ratanah If you can afford ratanah and don't mind that she is ELO banned now and then else go with Miken Moose.