In fact, accumulating BTC gradually is quite easy, and Bitcoin transaction fees aren't even a barrier. However, it is important to realize that this requires strong determination and fundamental confidence. If someone gradually saves or installs Bitcoin at a rate of $1 per day, it could grow to around $365 in a year. Well, it doesn't have to be every day,it could be saving fiat for 10-30 days and then exchanging it for Bitcoin, so makes it easier. Furthermore, if Bitcoin experiences a decline in value, this will be a discount or additional support, and can be an opportunity to accumulate even more Bitcoin. Hopefully, during that period, we might have additional income, whether from additional work/overtime, getting a project to work on, etc., which can also be used to accumulate Bitcoin in installments.
Your idea to buy slowly Bitcoin is great idea. It is simple plan that really works. Starting with small amounts like just dollar day is easy way to build up much of Bitcoin over time. Your idea to save up money for few weeks and then buy Bitcoin all at once is also good way to do it.
You are also right to see when price of Bitcoin goes down as good thing not problem. When price drops it is like sale and you can buy more Bitcoin for less money. Using any extra money you get to buy more during these times is very good way to grow your Bitcoin faster.