I'm in my 20s and I have some emergency cash stashed aside. My plan is to save up a separate sum of money just for investing, Am I being too prudent?

As you are still relatively young, so you can save up your emergency fund and investing at the same time. Its always good to start early as you have long runway to recover.

Yes, that is the right mindset. It is good to have at least 3-6 months of emergency fund. Only invest what you can afford to lose.

Hey! Education is the best investment, especially if you're starting late. There's tons of FIRE blogs are there, but if you're like most heartlanders in Singapore, with at least a 30 minute commute in the morning, i would suggest downloading the app Libby, where you can borrow ebooks from the National Library very user-friendly interface (wayyy better than the previous method of using Overdrive).

My top recommendation is the following book available as an ebook via Libby

Financial Freedom: A Proven Path To All The Money You Will Ever Need by Grant Sabatier. My personal review is that this book covers 95% of everything you need, including how to ask for a raise, how to start a side hustle, how to invest etc. If you need a great starting point, i think this is it. This was written by the blogger of millenialmoney.com and he also has a fairly informative podcast. Go check those out as well.

I guess i will end with: for almost anything, the best time to start was yesterday. But the next best time is today. And you dont have to start perfect, or start 100%, you just have to start. And i think the above book will give you more than sufficient strategies/tactics to get started in 90% the right direction.

Best of your luck.

Yes, I feel that the opportunity cost would be worth it as you should separate your life savings/emergency funds and money used for investments. Note that all investments carry risks and thus, only invest with money that you can afford to lose and diversify your portfolio to minimise the rise. You can take up SSB to meet the investment criteria to earn additional interest since SSB is safe and provides decent returns, killing 2 birds with 1 stone