Buy a little bit of bitcoin every week don't care if it's a $1, $5, $10, $100, figure out what you can afford every week and buy it, get rid of unnecessary expenses or whatever you can think of getting rid of and spend it on bitcoin
5 to 10 years if you buy some every week you will be a multi millionaire
As far I know the lowest amount that has been bought or sold is minimum 10$ .And if someone want to buy 10$ of BTC every week or month this will be not a bad idea , it's called micro assets collector.This will create a big asset one day .In every investment need to have a right time and proper knowledge about where will be invested.Buy hold and sell in right time this is the basic rules of become rich with BTC.