Sorry for not replying I was blacklisted and went slightly inactive.
Obviously this thread is mainly aimed at daily tournaments but you need general help and I will give it to you. You have 350k clintz I would suggest into buying a few solid clans you will enjoy and not get bored of. Do as many missions as possible and daily tournaments for top 150 (for 1 credit) and save 40 credits. From that point you want to start buying elite packs
and selling/keeping the cards you need/don't need.
Don't invest in cards - you're new to the game and need the clintz, you will of probably quit again before the cards you invest in are even worth reselling.
Don't constantly change decks - You will gradually lose clintz if you keep buying and selling cards to make different decks, buy a few clans or a few decks for different game types and stick to it.
Don't lose hope in the game and find friends and a guild to keep you from going insane, stick to one guild so you get all the bones from being in a guild. Learn don't envy, so many new players are so obsessed with being better than a player rather than learning what he did wrong and the other player did better, don't do that.
Anymore questions Pm me.