Is it worth to get so many cards for Miles?

Hi Anonymous, first up congrats on getting a job! This is the start of true adulting so hope you get to ace this miles game.
For fuss-free cards, DBS Altitude and Citi PremierMiles are great options to start off with. Their miles do not expire as well so huge plus to slowly accumulating these miles. More importantly, do not be compelled to spend more in order to accumulate more miles.

I found this article (https://milelion.com/2019/09/21/miles-game-star...) useful as to the different types of cards available to maximise all possible miles so hope it's useful for you too. Not to further confuse the mix with more options, but the idea is not to be restricted to just one single card when maximising the miles earned.

As you mentioned you can't clear those sign up bonuses, one of the easier ones I've encountered is the AMEX Krisflyer card. Currently you stand to get 10k miles through existing users' referral just by spending 1k in first 3 months, compared with 5k to 7k for most of other entry-level cards.

Happy to help you further if need be, and all the best in your miles journey!

If your spending is a lot. I think yes. If not, not worth the hustle to keep track for each card spending. That is for me.