You don’t need to buy anything just to make enough to cash out unless if you’re that desperate to get to $25 as quickly as possible. As other people have already mentioned, perseverance and patience is the key. You definitely will not be able to get far if you let yourself give up that easily.
I’m in my mid-twenties (unemployed, no children, no car or plans to buy one in the future) and I get disqualified from daily surveys just as much as you do. Being a perfectionist myself, I don’t handle rejections well, but I’ve had to force myself to get used to them when going through surveys and offers each day. Some days are great for me, while others are not. Daily cash mails and PTC aren’t available to me in Canada (yes, really… believe me), I get very little videos, and I don’t use RadioLoyalty because of too much music sitting on my hard drive, so I’ve had to rely on CrowdFlower tasks over the 4 months I’ve been here. I earn much more on another GPT, and CrowdFlower pays better there, but FusionCash has a better selection of tasks overall.
Also, if you find that you successfully completed an offer exactly as described in the instructions but do not receive credit after a good amount of time has passed, follow up with the offer provider with screenshots and/or proof(s) of confirmation. That means, for example, FusionCash support if you accessed the offer directly from the wall here. And if CrowdFlower is giving you a ton of grief with a particular task, go to its Get Satisfaction forum (accessible via Help > Get Support in the task) and provide screenshots / as much detail as possible along with your contributor and job IDs (also listed in the help menu). You worked hard to earn that money, so you should be paid accordingly and not be cheated out of your time.
So, in short: never give up, don’t lose faith, and keep persevering.