my friend already become a millionaire.
He is millionaire now by investing in Waves? That's great! I think Waves are too expensive today to start with. I tried it with Ardor but they are losing right now. Maybe, if price will fall below 0.08$ I will buy more. I know that's risky but I believe in this project as there is the Nxt team behind it. I think that the coin can reach 0.50$ or more in the future once some projects start with Ardor as main chain. But it's true, one should not put all eggs into one basket. Better split the money (if available) and put it into different Altcoins. And always watch for new promising Alts coming up (no "shitcoins").
Lending Bitcoins is currently not so much profitable as interest rates are very low. I saw that lending Clams brings much higher interest rates but changing your BTC to Clam is also risky. What if BTC rises more and more in prise and your Clams not? It's not so easy. Better take the low BTC interest rates and wait for better times.