I think the best strategy is to split this amount into two parts for example 3,5 and 1,5. Buy 7-10 different alts from top 100 on 3,5 and 1,5 keep for promising ICO (~200-300$ on each). My favorite alts is ETH, ETC, NEO and LSK. They are all very stable and promising coins and the main advance is that they got own blockchain that allows other apps use it, and I think we will see a lot of more new projects in the next years based on those blockchains.