User blog comment:YuichiroHyodo/Brave Frontier tips/@comment-32619294-20170806104414

for new players, especially f2p, i don't recommend using gems for refilling your energy with gems. prioritise those gems for expanding item and unit slot (it is good to have 10-20 empty slot on item and 20-30 on unit storage), and like the tips says, save up your gem for a really good banner that has lesser amount unit (ex : only support gate, mono elemental gate, resummon gate, etc). refilling energy is easy if you always leveling up.