I have to agree with "not just one coin", but buying to much different coin wont be effective to earn profit as some of them may not give you profit or even give you loses. If you want to do so then you should not use the same budget for each coins you are going to buy IMO. Give more budget for the coin that you really believe will give you more profit or coins that has the best possibility to raise significantly and spend less money on the other coins.
Top 10 coins does not mean that they will always give you good profit.