Definitely upgrade heros skill after you get a good set of core heros. In your case Champ and Paladin are not good, except for situations. Once you get Immo, you should be able to farm higher levels of HBM and dungeons. GR is also excellent for both. Focus on leveing Druid, TG, and Aries; and do not bother leveling up Champ or Paladin untill you have lots of excess HB.
FYI, the big jump in shard farming is when you can farm dungeon 8. Then you can farm 500-1000 shards per day just from d8 alone depending on how much you play. Level up your core of Druid, TG, and Aries. Farm or roll for Immo and GR; and hope for PD or Cupid. You should be able to start farming d8 when their levels are around 120... depending on how good their talents and skill levels are. Good luck.