300$ for me is enough to start investing. You should part it to less than .5 $ coins to make make it realistic. Maybe 100$ in one ICO, 100$ to other, and 100 $ to other. More choice much better.
For that he has to invest in 3 altcoin with the amount of 100,that's a little less good in my opinion even more if the investment in ICO that most of the options may sometimes be a bad one feared if one invested in a damn project.Its better to divide between 150 for one project in my opinion to be more focused on advancing the project.