I have doubled or trippled my effort many times. I try to look for coins with an market cap beneath the 10mio mark. Look for an coin with a good product, whitepaper, solid team and roadmap. Put some money in (split over multiple coins) and just wait. When it dips 10 or 20% just let it sit. Once it gains 2-300% (or higher if you think it can grow more) and sell. Do this over and over again and you should be able to get some profit.

If you are not sure what to choose, and want to do it save. Pick a top 50 coin and invest in that, en let it sit. Cardano, Stellar and Tron are still working on their product. Stilll room to grow .

Good luck!