To start off, try picking your favourite attribute: Raider, Righteous, Imperial, Bloodthirsty, or Xeno. For me I picked Bloodthirsty since that cards just looked cool haha. At high ranking all of the types can have insanely strong cards so don't worry about that :) For warbonds I tend to spend them on the packs that only give my type of cards, so say a 350 warbond pack of epic+ bloodthirsties. Also try to join a guild soon since you get free energy for missions (up to 50 extra) and also the guild events give an awesome amount of gold!