Like with any occupation, if you don't invest the time and effort in learning what to do and how to be good (preferably great) at it it's very hard to keep doing it. In order to invest enough time and effort when you start out in domaining, I feel like you need to have a passion for words and branding and preferably at least a decent grasp of the English language (unless you're targeting non-english speaking countries). Even if you have a decent budget to begin with, which most people don't, you have to understand what to buy and at what price, otherwise you might as well go to a casino.
If from the get go you don't enjoy playing around with words, recognizing why some combinations are better than others, digging into data, experimenting with different sites that can help, have a passion for hunting for gems in piles of crap, staying updated on trends etc.- you won't put in the amount of time and effort that are required in order to learn how to do it well and then you won't be able to upgrade to better names.