I think 400$ is enough for trading. You can buy cheap altcoins that has big potential in the future. Before buying you need to study and research and try to diversify your money by buying 3-4 altcoins.
Altcoin in this market is easy to be dumped. It's not going to be profitable for you. In my opinion, it is best to buy the top 10 coins in the rankings, although the profit is low but safe. Then, you can join the Bounty campaign to gain a better understanding of the market.