1st you can practically start at any amount you want, there is no minimum or maximum amount in buying altcoins, unlike the traditional trading wherein there are boardlots you need to meet before you can buy shares. My advise is if you are a begginer and just would like to test or try buying some altcoins start with an amount that you are comfortable loosing. i am not saying that you will loose your money when you buy altcoins but buying coins is a high risk especially that the market is highly volatile, it can make you or break you. invest in small amounts until you get the feel and confidence. Once you are confident enough now you can invest big but be sure to stay on budget, avoid making debts just to invest i would recommend to us your hard earned money in investing. You should also start researching first historical data of the coin you want to invest in if it has some potential to earn you money, researching before buying will go a long way.