Buy a little bit of bitcoin every week don't care if it's a $1, $5, $10,
Buying $1 every week is going to be difficult with today's fees. Also, you won't make any money investing $1 or $5 a week.
Just do the math for $5: In a year you're going to have $240, $2400 in 10 years. Even if bitcoin goes up 10x in this period, all you're going to make is less than $24k, so in 10 years you'll save up enough for a used car.
What I'm trying to say here guys, invest life changing money. You probably won't get another opportunity like this. Don't DCA $5 because it's not going to make your life better.