There are lots of ways for the poor to participate and I have a few friends from India who do so,they can claim a lot of faucets daily,watch videos,do the Paid to click sites and so on,they have a section here in the forum called "Micro Earnings" which is exactly for people looking to start and find new ways to make some extra money.Beside this I think everyone or almost everyone has at least a decent GPU-graphic card to try and mine some altcoins and keep them in their wallet.
And last but not least as already said anyone can buy as little as they want,usually 0.0001 Bitcoin as a minimum which is near 5 dollars right now.
Bitcoin is really expensive compared to other crypto coins but knowing how high its profits will be, then its always a must buy. While you are earning to buy a whole bitcoin, maybe getting a portion of it is already good as long as you can manage the amount once its lose. But investing in bitcoin for long term will definitely give you more assurance to be profitable as long as you're patient enough to wait for its price to surge high.
Bitcoin is not made for rich people but definitely for everyone in the community. The poor ones may find it hard to start buying bitcoin but if you really want to invest in a promising coin, the price is worth the risk. There are a lot of ways to earn bitcoin. Just explore the whole crypto market and you'll eventually discover that there are plenty of opportunities around.