I'm in your same situation, need 4 yellow 3* shard to upgrade soldier to 5, in a week i got two. I understand the grinding, i put game in automatic and ok, but it is very, very difficult. And i don't want to spend money, sorry, because even if a buy 30 legendary souls the drop rate of the best chara is so low that probably i'll just waste my money (i read what happened to those guys that choose to buy souls). So yes, i', with you too.