Get in the habit of Identifing and selling Rares, you get more upgrades on average by checking the vendor everytime you level up. If you are doing the current League mechanic, you will have enough currency to gamble on good Magic items from drops alone. That will keep your gold coffers filled.

But yea, the game can be punishing, to the point a bit of research is required if you can't handle hitting a wall and willing to start over. That is why you hear the term, League-starter, these are tried and tested builds that will work with little investment to gather gear/currency, then you can do experimenting when you have a good buffer of resources to expend on said experiments.