As others have said get into a good guild. If you are constantly one of the top earners in your current guild you need a more active one.
As for goals, I would say to aim for getting all kingdoms to 5 stars, then 7 stars etc. Requirements here:
Another goal that you can work on simultaneously is to fully trait and level all the troops that you have. Farming explore with The Dragon Soul will be your best bet in this regard.
Purchasing the Deathknight Armor will be the best investment you could make in GoW for long term benefits. If you are really enjoying the game and can see yourself playing for years to come I would highly recommend this purchase.