Any amount is suitable for a new investor to start investing. Even a small investment of as little as $10 can kickstart their investment using DCA. The problem is that some cannot keep up with that $10, after some time they get to stop investing in Bitcoin. But come think of it, $10 is quite a comfortable amount for anyone to be able to DCA with. Any investor who can't keep up with a minimum of $10 investment every week should not be investing in Bitcoin.
To make it very clear, every investment has risk, and Bitcoin does, too. There is no guarantee of success in any investment, so when we are talking about dca and buying for hodl if it is not properly done, the right way, an investor might lose in his Bitcoin if he sells at panic times.
Bitcoin investment is not for everyone morespecially if an investor don't have a disposable income, even if the investor has as little as $10 as the op made mention of, so long as it is not discretionary Income that is money he will not be needing for a long time he is not fit to invest in bitcoin. So many thinks as long as they are holding bitcoin for a long time that there investment in bitcoin is bound to be successful which is wrong however bitcoin investment is best appreciated when view in terms of long term.