Honestly, it's going to be hard to make money with that small of an initial investment. You really need to get lucky and get in on one of the coins that double in a day like DGB, OMNI, BCN have done randomly over the past couple of weeks. Siacoin had a +30% day yesterday but that doesn't necessarily mean it will do the same again this week. DGB is pretty cheap at the 1200 sat level these days and they just released Emma AI so that could bring some rise in price over the next few days. Who knows, but you aren't really investing when you are starting with only $15