Well to me I don't really see any thing wrong with that, starting with $10 if that amount is one's discretionary income since it is not advisable to invest money that will be needing for our daily expenses into bitcoin so instead of waiting for our discretionary income to increase while we are a no coiner or a low coiner starting with $10 discretionary income won't be a bad idea.one can be accumulating bitcoin with $10 and at the same time while working on increasing his discretionary income .
Trying to run an investment with a fund of $10 is clearly okay as long as it can be done routinely every week by the person running it and it can also be considered as a form of his own business that he started from small to become more when it has been collected slowly through the $10. Because the goal itself is to buy Bitcoin with the existing level of ability and it will also become more over time so there is nothing wrong with that because a better investment method is when someone wants to do it comfortably without sacrificing anything to himself except for capital and time.
But I have also seen someone who tries to collect money to become more before he uses it to buy Bitcoin. The only downside to this method is when the price of Bitcoin starts to increase and he still hasn't bought it, so it can also be a loss for him because he has delayed buying because of the amount of money that has not been collected as he wanted.