There are only two ways to invest in bitcoins from some topics I have read in this forum, to buy a big amount of bitcoins once and to buy small amounts regularly according to a plan.
Buying big - Although this is generally not advised, I think buying big can be good if you can afford to buy big and then follow up with adding small amounts to what you have. Buying big will help you get a good amount of bitcoins quickly.
Why do you thing buying big is generally not advised? If you are having enough money and you have done your research and you believe that’s the best time to buy, you can just buy at once and leave it in your wallet, actually I will recommend this for people that are planning to hold the bitcoin for long time, you don’t have to start studying the market just because of $1 or $2 difference, the only people that should be studying the market frequently are the day trader’s, but if you are holding for long time, just do your analysis and know when to buy.
Buying small occasionally, otherwise known by the name of dollar cost averaging - This is method that is advised for people who are not rich, and who do not have enough money to buy big. I think if you have enough money to buy big and follow up with buying small amounts, but you just decide to buy small amounts regularly, you are not doing the best for yourself.
Buying small occasionally is not a bad idea, maybe you are the type that’s been paid daily, weekly or monthly, you can be removing from part of your salary and buying bitcoin with it, no amount is too small to invest in bitcoin and no amount is too big to invest in bitcoin, but invest any amount you can afford to lose and don’t invest any amount that will hurt you after investing.