You're probably having unit bias; where you consider the potential of a coin based on how affordable a whole is. It looks better to own 31ETH than 1BTC, and with the same amount you can purchase of other altcoins. This however is not how the market works.
With $50 you get about 0.002BTC, seems small if you can get about 50 of xcoin for the same amount, however if the fundamentals of Bitcoin is stronger, it would be far more profitable in the long run and you will get the exact same ROI as someone who owns 1BTC and that would be far more than someone who holds 50 xcoins

You do not need to own an entire Bitcoin, create a buying plan and purchase based on that. Remember to only use amounts you can afford to lose