Shop You can avoid using the shop later in the game to break down and buy gems in order to restore your Mana or Stamina if you are frugal with your items early on.
Quests Make sure you do quests whenever possible and if you get stuck on a quest because you are in a fight and do not have enough Mana you can revisit earlier quests to get some. Doing quests will increase your Experience and there will be times you will earn small Stamina and Mana refills along with plenty of rewards when you have collected ALL the cards in a zone.
Treasury Make a point of always checking your Treasury when you have been questing for a bit so you know exactly what you have and what you need to get.
Maximise Card Stats If you fully enhance your cards before you evolve you will maximise your cards stats. It also helps to evolve higher evolutions with their duplicates.
Heavy-Hitters When you go questing it is not beneficial to put ALL your heavy-hitters in your deck because the amount of Mana that is needed for each fight when you use a party full of powerfull cards will not be cost effective and you will just end up spending a lot of time waiting for your Mana to recharge.