This has been one of the most asked questions asked by newbie traders or people who want to try trading to make money. If you know the basics then nothing is a small investment. Even 0.005 or 0.01, approximately 10 - 15$ is enough to start. The main point to remember is not to be greedy at first. Build your principle amount and then try experiments.
it is true and i am agree with you, with the bigger money you use, there is a big chance that you can make a big profit too although this is not always guarantee that you will make big profit but at least, with big money, you can buy bitcoin or altcoin in big amount too and if the price is going to increase, you can be prepare to sell the coins and maybe you can make big money too.
beside that, you should think about the risk that will always follow with big funds in trading and you should thinking this as your learning in trading so at least, if you get loss, then you have a good lesson that you will not doing again in future.