Is it better to invest one lump sum into different stock (and bonds) or spread it across many different months?

Hello there! I noticed that your available capital for investing is limited in 4 digits range. Hence I understand your concern in brokerage fees stacking up if you DCA.

I would suggest NOT to DCA and NOT to diversify, ie. max 1-2 stocks in your current portfolio.

While saving some fees is one of the reasons, I encourage you to study deeply in the stocks that you are interested in, and buy the one you have the highest conviction with, while being prepared to hit a wall.

Investing is never easy and is a life long learning process. As an amateur, you are more likely to make mistakes in your first few investment decisions, and you can learn from the mistakes with minimal capital. This will speed up your long term personal growth in investing, instead of succumbing to the easiest way (DCA and ignore) at the start of your investing journey.​​​

You are right that the commission fee of $25 takes up a significant percentage if your trade size are say in the low 4 digits. I am currently using FSMone which charges S$10 per trade for SG stocks and US$8.80 for US stocks. There are also brokers like Saxo and Interactive Brokers(IB) which charges less trading fees than $25. These brokers maintain your holdings in a Custodian account which is not the same as your existing broker which I believe maintains your holdings in your CDP account.

To know the difference between CDP and Custodian account, please refer to an article by Seedly here.

For a comparison of trading fees of stock brokerages in Singapore, you can refer to this cheatsheet by Seedly here.