Depends on your circle of competence and how deep you are into it. For example, if you work in tech, participate in tech meetups/conferences regularly, rub shoulders with tech people all the time, you probably have some special insights into tech, and you may find it a lot easier to predict the success of tech companies much better than most. Of course, you should still do some basic research into the financials and management of the companies. There are 4 key principles that you should focus on:
(1) Buy into companies that you can understand
(2) Companies have honest and able management
(3) Companies have a competitive advantage that's likely to last for the next 10 years
(4) Calculate a sensible and attractive price (which is dependent on your desired ROI for the next 10 years).
Point (4) requires some explanation: For example, if you are only looking looking at 10% returns per year and let's say you are buying the stock at $100 today, the stock price will need to reach $259.37 in ten years. Based on (1), (2) and (3), you should be able to work out some reasonable estimate for the stockprice/intrinsic value of the stock. PM me if you need more clarity.
Don't worry, I still feel the same way even after an entire year's of consistent reading and studying Finance modules within NUS! I think it really depends on how you want to be investing, and what kind of assets you are actually investing in.
Passive investing methods such as placing money in a trusted broad based index fund Like a Vanguard S&P index fund requires almost no prior financial knowledge but long, long patience and trust in 1 thing - the power of compounding, the "8th wonder of the world". You don't need to understand what the companies that make up the S&P do at all, you just have to check back one in a while, make sure the fund performance is extremely close to the S&P index, and trust that America's Wall Street and currency remains the backbone of the financial industry, which it has, and it most likely will.
Active Investing on the other hand, will require alot more information. If you are unable to really justify with valuation evidence that a certain stock is good to buy, unable to understand what type of macroeconomic news affect particular industries, I think you still lack research and knowledge in the fundamentals. Strong fundamental knowledge in Relative valuation ratios, Balance Sheet/ Cash Flow Statement and Industry averages is crucial in investing. These information allow you personally evaluate whether a company is doing well/badly RELATIVE to other companies, because performance is always relative, and whether the stock price is overvalued or undervalued. Having your own evaluations during active management is extremely important in ensuring that you are able to trust your own judgement, and not have to solely base of other's. From there, you will be in a much better position to invest!
Put yourself in a position of a stock pitch - if you are unable to pitch to yourself the reasons why you should buy the stock and back it up with strong evidence, why are you even thinking of buying the stock in the first place?
I wish you all the best! the journey is never easy, because markets are always changing, and new information comes nearly everyday. But you don't have to know everything, just the most vital ones, and NEVER invest emotionally!