I don't understand what you mean by diversify little by little, because from what I understand about the word diversify, it means to stop your bitcoin investment and put the funds that you are using to invest in bitcoin into another asset like stock, bond, gold or real estate.
A new investor shouldn't think of diversifying into other investment but rather he should stay focus on building ans growing his bitcoin portfolio overtime, because bitcoin investment is already outperforming other kind of investment both physical and digital in the market. Trying to diversify might make you lose focus and make thw wrong decisions that will lead to regrets. It is when you have accumulated more than enough Bitcoin and you feel you are not secured with only bitcoin, you can diversify into bonds, properties, cash equivalents and stocks.
As a person who has spent some time in Bitcoin, I would fully agree that Bitcoin must be our core focus and we must be bullish in bitcoin accumulation (if we don't have enough Bitcoin in our wallets). That's because over period of time I have developed my confidence in Bitcoin and I know that in long run Bitcoin has fair chance of going up.
But I think a new investor who is coming from other areas like stock or real estate might not have that much confidence in Bitcoin like a person who has sent some time in Bitcoin. He will take his time before he fully understand the benefits of investing only in Bitcoin.