I am a newbie and would like to invest $1000 to start.
Do you already understand enough crypto investment? I think since you are a newbie, you should focus on learning first. The focus shouldn't for gaining as much as profits. $1000 is too big money to use for your start, just use smaller amount of money. $100 is enough for your early investment, the focus is on the learning. But if you think that you already have enough knowledge and experience, $1000 is no problem to use as your capital.
I have read that I should put 40 percent into bitcoin and diversify the other 60 percent.
It depends on you, it is not a must. You can use 100% on Bitcoin, or you can diversify to top altcoins. The point is you choose the most recommended coins to invest only. Top altcoins such as BTC, ETH, BNB, ADA, SOL, MATIC, TRX, and DOT are the most recommended coins for investment.