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
Bitcoin is obviously an expensive investment, most especially if you are trying to accumulate the whole piece of it. But if you are trying to do dollar cost average regardless of the amount, you will not feel the expensive price anymore as you are only investing every now and then the amount that you can afford to lose.
However, the only thing that you should worry is that if you are not patient enough to hold for that long term. DCA will be useless if you suddenly resort into panic selling everything the market is crashed due to market price correction.